Since dried buhkser have a long shelf life they are very prone to bugs & need bedikeh.
If I remember correctly the prepacked Tu Bshvat assortments with
Hashgacha haven’t had buhkser for ages
personally I doubt it has anything to do with Minhag Yisroel & RASHBI’s carob tree. Very simple this time of year there was no fresh fruit to be had & buhkser was just one affordable dried fruit