The problem definitely still persists, HOWEVER, I've noticed some commonalities. They're definitely trying to make your life easier even if it sometimes fucks up.
I have a way to reproduce the issue reliably. If you subscribe to someone who regularly releases things in multiple parts close together. Like imagine 3 20 minute videos that come out about 20 minutes apart that when combined make a 60 minute video. Only the first one will appear in your subscriptions.
IF this always worked perfectly I'd have 0 problems with it. It does not, it sometimes genuinely hides things you'd have wanted to see.