I can give you a funny example of this. Of my entire collection (12) I have had 1 impacted frog. I fed him normal size food items and had him on eco-earth, yet he was impacted and it took several honey baths to help him poop it out tiny chunk by chunk.
Now, I have 2 females that are exactly 4.3" both. 2 weeks ago I fed all my frogs adult locusts, both my adult females (wich are the biggest in my collection) were backed up and required a honeybath to poop it out. While the small ones (as small as 2.7" males) did not have a single problem. This shows that size doesn't matter, it can happen to any frog but size does play an important role when feeding extremely large feeders, because they massively increase the risk.