The clip link opens a plain YouTube player that begins at your start time and stops at your end
time. It is playback control, not a real trim. The scrub bar is still there, so they could drag
past the end. Good for "watch this bit", not a way to hide the rest of the video.
Shorts: a Short's clip link plays in a normal landscape player, not the vertical Shorts feed.
The right part plays, it just doesn't look like Shorts.
If a creator has disabled embedding, the clip link shows an error for them. Send the fallback
link instead. It opens the video normally at your start time.