About four years ago, I was helping a guy who called himself The Affordable Handyman. The first job we worked was filling one inch gaps in exterior trim.
To my amazement, he filled the huge gaps with latex caulk, without any foam or other backer. Needless to say, if it didn’t all fall out (it was cold enough out the caulk was thicker, so stiffer than usual, it was going to shrink a lot, as it dried.
To add to matters, the genius, in the course of caring for his customers, insisted I paint it, just as soon as he was done filling the gaps. He got miffed when I refused (I could never pull that kind of crap on a customer).