Galaxy S22+ here. It doesn't seem like a lag issue, more like the animation was meant to delay for a beat after you tap. Agree that it's not a major issue, but it delays long enough to make me pause to confirm it actually registered the tap.
ETA: it's only on post up/down votes. Comment votes have a different animation that is immediate, and which I'd prefer to be used for posts as well.
Yes the upvote and downvote buttons start a blue spinning wheel while it's doing something, and then shows the updated vote count about a second later.
It doesn't have to do with the phone. Probably it's waiting for a response from the server before it registers the vote, and that takes a while.
Edit: For me the animation starts right when I click, it's not delayed. Only the updated vote count is delayed. So maybe it's not the same issue as you are describing.
On my Samsung Galaxy Z Flip 3 I also noticed it takes a second or so after tapping before the animation even starts. It's not unbearable or anything, but it's enough to make me think that I missed the button and try tapping again sometimes.
The bookmark animation looks a tad faster to me. The options menu animation prompted me to request the option to disable animation effects since I use that fairly often. 😅
That setting should just be for Android system animations. So the animation when switching to or from Connect to another app; for example, these kind of animations would be affected. But animations within the app would need to be adjusted by the app. The dev is pretty receptive to requests and this has garnered a fair amount of support so I think they'll shave off a few hundred milliseconds from the animation to make it look more responsive.