What I do observe from your posted image is that in the top track you have audio in negative time - see the little arrows at the left of the track.
So my next test
Generate a 3 minute chirp
drag the clip leftwards so that 15 secs is before T=0
st the cursor at T=15
Shift + J
Observe: selection extends over negative time -15 to +15
This I believe is correct behavior. The keyboard prefs for Shift+J says of that shortcut “Region Track start to cursor”
which is the command Select> Region>Region Track start to cursor
And the Manual says:
Track Start to Cursor Shift + J
Selects a region in the selected track(s) from the start of the track to the cursor position (or extends the current selection so that it starts from the start of the track).
And since the track now starts at T=-15secs the observed behavior is correct and expected. I would also expect the deletion to work on the selected part of the track that is in negative time.
The big question is just why you have audio in negative time?
As what I observe of your behavior is correct and expected too.