This issue is an old one. Back in the 1970s when I started my bike shop life we had hard to mount tire/rim combos. These days we still do. I won't be the one to say that any country of origin having no consistent aspect, rim or tire. having said that some brands do seem to be closer to one end or the other end of tolerance range. Conti being one on the tighter fit end of tolerance often. But I've found it's the rim that has the greater design contribution, how deep is the bed. Since rims are made in batches of 10 (or so usually) the same rim model can see drift from intended spec far more readily then the thousands of tires coming out of the same mold.
I have offered customers the chance to mount the various tire offerings we have to find the ones that they can handle WRT the actual rims on their bike. We also try to keep in sock the Kool Stop tire jack, but don't sell many as they're not needed often.
I'm 65 years old and still will come across a really hard to mount combo. But being a guy and a pro wrench it's a matter of shop pride to avoid a tool to mount
Andy