I put 2.2" tires on my Dahon Jetstream and take it on lots of "unpaved" tracks. The Jetstream has many features that make it better than most folders. Front and rear suspension, disc brakes, a large frame bridge section and hinge, triangulation on the seatpost tube including a tall seat post tube, and short handlebar post. All add up to make the bike quite capable.
If you want more surety it is easy to reinforce the hinge sections. I would do that with any folding bike if I was doing long tours or generally putting more repetitive loads and stresses into the system.
There are very few of these bikes still in the USA network. I've got a few of them.