How can an INNER / RIGHT / LEFT JOIN be 14 times slower than a FULL JOIN?

I have a query that takes 2.5 seconds with a FULL JOIN and 40 seconds with an INNER, RIGHT or LEFT JOIN.

Here is the request. A subquery (performed twice) takes only 1.3 seconds.

SELECT T1.[time], T1.Total, T1.rn, T2.[time], T2.Total, T2.rn
FROM
(
select [time], MAX(ComputedValue) as Total, row_number() over (order by [time]) as rn
FROM
(
    select SUBSTRING(CONVERT(CHAR(10), IntervalStartTime, 108), 0, 6) as [time], ComputedValue
    from LoadTestTransactionSample
    where LoadTestRunId=285
    and CounterName='Total Transactions' 
    and TransactionName='Export'
) foo
group by [time]
) T1
_____ JOIN
(
select [time], MAX(ComputedValue) as Total, row_number() over (order by [time]) as rn
FROM
(
    select SUBSTRING(CONVERT(CHAR(10), IntervalStartTime, 108), 0, 6) as [time], ComputedValue
    from LoadTestTransactionSample
    where LoadTestRunId=285
    and CounterName='Total Transactions' 
    and TransactionName='Export'
) foo
group by [time]
) T2
ON T1.rn = T2.rn - 1

The bit select SUBSTRINGjust gets the string HH: MM from DateTime. LoadTestTransactionSample- actually VIEW, which is combined through 8 tables. (FYI database is a repository of Visual Studio boot test results). Here are its columns:

LoadTestRunId INT NOT NULL
CounterName NVARCHAR(255) NOT NULL
TransactionName NVARCHAR(64) NOT NULL
IntervalStartTime DATETIME NOT NULL
IntervalEndTime DATETIME NOT NULL
ComputedValue REAL

FULL JOIN returns an extra unwanted string, so I need to RIGHT JOIN to get the correct answer.

( : SQL Server 2012 'LAG', @a1ex07), , .

EDIT: . , .

2: 45% 55%, ( 99%/1%). , , .

3: :

(40 row(s) affected)
Table 'LoadTestPerformanceCounterCategory'. Scan count 0, logical reads 37556, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'LoadTestPerformanceCounter'. Scan count 0, logical reads 176464, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'LoadTestScenario'. Scan count 0, logical reads 176464, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'LoadTestCase'. Scan count 0, logical reads 176464, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'WebLoadTestTransaction'. Scan count 0, logical reads 13411100, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'LoadTestPerformanceCounterInstance'. Scan count 0, logical reads 36563718, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'LoadTestPerformanceCounterSample'. Scan count 19721, logical reads 269657, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'LoadTestRunInterval'. Scan count 41, logical reads 205, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

SQL Server Execution Times:
    CPU time = 36754 ms,  elapsed time = 36763 ms.

:

(41 row(s) affected)
Table 'Worktable'. Scan count 0, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'LoadTestPerformanceCounterCategory'. Scan count 0, logical reads 1832, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'LoadTestPerformanceCounter'. Scan count 0, logical reads 8608, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'LoadTestScenario'. Scan count 0, logical reads 8608, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'LoadTestCase'. Scan count 0, logical reads 8608, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'WebLoadTestTransaction'. Scan count 0, logical reads 654200, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'LoadTestPerformanceCounterInstance'. Scan count 0, logical reads 1783596, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'LoadTestPerformanceCounterSample'. Scan count 962, logical reads 13154, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'LoadTestRunInterval'. Scan count 2, logical reads 10, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

SQL Server Execution Times:
    CPU time = 1950 ms,  elapsed time = 1944 ms.

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