@NJCS13 In our experience, what you’ve previously heard is accurate: fighter pilots can transfer to heavies easily, but not the other way around. There’s no rule precluding heavy pilots from becoming fighter pilots, and there are (very rare) examples of it happening, but it’s uncommon due to the amount of retraining (ie time and money) a heavy pilot would likely have to go through.
Fighters to Heavies only requires completing the 4-6 month transition course in the new aircraft (ex: C-17 school) and the squadron would get someone with a lot relevant flying experience.
Heavies to Fighters would require going to 15-18 months of training (the centrifuge, T-38s, IFF, and then a full fighter B-Course), and after all of that the squadron would still get someone with very little relevant fighter experience and less time to develop that skillset because that person already used up part/all of their initial pilot training commitment from their time in heavies.
Ultimately, however, if you’re applying to a Guard/Reserve fighter squadron, you just have to convince one squadron that you’re right person for the slot, so anything is possible.