Still an issue for 1.18.2 on Switch at least. As for reproducing it just put an observer right over a nether wart plant, turn the random tick speed up to 400-500 or so, then watch as it grows and the observer doesn't activate. The expected result is that it should send a pulse for each stage of growth (three I believe). As of right now it does not emit any pulse except for breaking and placing.
I have also had this problem while wearing an eyltra while I have been in end cities. It seems that exiting the world and going back in fixes it for a while but I haven't found anything to prevent it.
Still an issue for 1.18.2 on Switch at least. As for reproducing it just put an observer right over a nether wart plant, turn the random tick speed up to 400-500 or so, then watch as it grows and the observer doesn't activate. The expected result is that it should send a pulse for each stage of growth (three I believe). As of right now it does not emit any pulse except for breaking and placing.