Once I did this on one char the hooks for this seem to be dismantled for other chars,
like certain drops seem to no longer drop, things that could be picked up aren’t there, etc
I know there’s no real point in doing it again, it’s just passively I had a couple other chars there were about 2/3 done, I thought I’d finish it out
question – is this some account level 1-off? like as it seems, once it’s done it’s no longer present for other chars?
Once you’ve obtained a mount you can’t get it again. There’s no point at all in keeping any of the bits.
Eh, this isn’t accurate. You can obtain many mounts many times. Prime examples include the covenant renown mounts, mounts that drop from mobs, etc… There’s also plenty of BoE mounts you can craft/obtain over and over again for gold-making purposes. You can’t learn any mount more than once though.
As for the rings themselves, certain rings aren’t available at certain times. For example, the Stone Ring is only available when the quest “Putting a Plan Together” is up in the Necrolord Assault. The drop rate is ridiculously low as well, but people often put the ring quest up in LFG for sharing 
I will agree with Moonphyre though. Once you have an account-wide mount, you’re finished in that regard. Even if the other rings aren’t showing up due to a bug, I highly, highly doubt that any effort would be put into fixing it considering it has no negative impact.
With that said, if you feel there is a bug occurring, you should report it to the Bug Report forum so the proper eyes can see it.
it’s more something just on a whim, and seems odd that the stuff isn’t there, but yeah, I could put in a report