Clamping the playhead to the seek start time should avoid using an additional offset when possible.

[tdrews]

For live content, if the playhead is clamped to the seek start time then it's clamped with an additional minBufferTime seconds offset to ensure the stream has time to re-buffer after clamping (so the playhead doesn't move outside the seek window during re-buffering). However, this offset is not always necessary: the clamped location could already be buffered, or minBufferTime seconds may be large enough such that the playhead will jump ahead noticeably when trying to seek near the beginning of the seek window.