While I had hoped to get this in TeX Live 2021 and think that especially
since it's a corner case and the old behavior is clearly wrong, it
shouldn't cause compatibility issues, I completely understand your
position and will adjust luaotfload not to rely on it for the time
being.

By the way while working on this I thought that it should be relatively
easy to add a variant of init/select (init/chained?) which allows an
arbitrary number of such discretionary nodes (e.g. f\-f\-f\-f\-f in a font
with ligatures for upto fffff) as long as only one of the breaks can be
taken at a time (which seems like a valid rule in all reasonable cases).
This would be very useful for our HarfBuzz support code. Is there any
chance to get this integrated? (some time after the freeze of course)
I can provide an implementation but I wanted to check if there is any
interest first.