I had a bit of a hmm moment when I read about Fomapan 4x5" film curling.
I am on my third 4x5" box of Fomapan 400 with 50 sheets to a box, so I've processed at least 100 sheets.
The first box and about 75% of the second box were processed in my Jobo using 2509 reels and rotary processing, meaning they were curved/bent during processing. I have just checked my negatives, they are all flat as a tack. I don't remember ever having any curling issue using these negatives in an un-glassed negative holder in my enlarger.
The rest of the Fomapan 400 negatives have been processed in my SP-445 processing tank. This tank is an inversion type of processing unit, the sheets are held in a flat holder. These negatives are also flat as a tack.
I cannot remember ever having any curling issues with 4x5" or larger sheet film that I have used. Fomapan sheet film is all on a clear polyester base, which is 0.175mm thick. The Bergger Panchro 400 is also coated onto a 0.175mm thick PET base. Ilford has the thickness of the base of their 400 HP5+ film at 0.180mm. Ilford FP4+ is also coated on 0.180mm stock. These are the current films I have in stock and am currently using.
I found all of those measurements from the respective manufacturer data sheets.
I don't think any sheet film would curl, unless it has been dried at temperatures exceeding about 50ºC and then aggressively dried. We once had a drier fault and the cabinet was blocked. The temperature went quite high, how high we don't know, but everything was too hot to touch. All the roll film, 120/135 curled like crazy, the sheet films didn't fare too well either, we were able to get satisfactory prints from the sheet films, but I seem to remember the 8x10" stuff had a distinct twist and was only enlargeable in a glass carrier.