Maybe they ran out of uncrustables because they were so busy with the EE previews? We were there on Saturday at 11:30 and they had the uncrustables then....
I can't comment on PB&J in the parks, but my DS ordered one at Whispering Canyon at WL back in November and it was on regular bread. What about the Plaza at MK? Anyone know if theirs is on bread.....since they serve mainly sandwiches there anyway?