Throttle(Time) interval difference between v6 & v7 when trailing=true

[fatsu]

Describe the bug

Throttle(Time) behavior is significantly different in v7 compared to v6 when 'trailing=true'.

In v6, only the triggering event/value from the source observable started a throttling interval. Now, in v7, the emitted trailing value also starts a new interval (acting as leading?).

This means that the throttling intervals for a given source-stream / (time-)interval will be different depending on how 'trailing' has been set.

Given the changed spec file (throttleTime-spec.ts) this might be wanted behavior, but I cannot seems to find this in the docs, nor is it mentioned as a Breaking Change.

Given the current behaviour, the image shown on the ThrottleTime doc page is no longer correct... 'C' value will no longer be emitted, but there will be 2 'X' value emissions instead.

Expected behavior

The same behavior as in v6, or f this is wanted behavior, clear documentation.

Reproduction code

// TEST (trailing)
    const source /*         */ = 'A-----B--C--DE------';
    // throttling_v7_1         = '----|               ';
    // throttling_v7_2         = '    ----|           ';
    // throttling_v7_3         = '        ----|       ';
    // throttling_v7_4         = '            ----|   ';
    const result_v7 /*      */ = '----A---B---D---E---';
    // throttling_v6           = '----| ----| ----|   ';
    const result_v6 /*      */ = '----A-----C-----E---';


    const result$ = cold(source).pipe(
      throttleTime(4, rxTest2, { leading: false, trailing: true })
    )
  
    // TEST (leading/trailing)
    const source /*         */ = 'A-----B--C--DE------';
    // throttling_v7_1         = '----|               ';
    // throttling_v7_2         = '      ----|         ';
    // throttling_v7_3         = '          ----|     ';
    const result_v7 /*      */ = 'A-----B---C---E-----';
    // throttling_v6           = '----| ----| ----|   ';
    const result_v6 /*      */ = 'A-----B---C-D---E---';
  
    const result$ = cold(source).pipe(
      throttleTime(4, rxTest3, { leading: true, trailing: true })
    );

Reproduction URL

https://stackblitz.com/edit/rxjs-y882mh?file=index.html

Version

7.5.7

Environment

No response

Additional context

No response