Eh. Who needs such bechira? Hashem didn’t seem to care much for it at Har Sinai. They tell us we’re supposed to yearn for mashiach yet they say Hashem’s existence will be obvious then. It’s a cop out.
I don’t think we should be deciding which nisyonos HKB”H should be challenging each dor with, but it’s clear that He does give a different set to each generation.
It’s also clear that many do find various scientific assertions challenging, and it would be folly to say that HKB”H didn’t know that this would be a nisayon. So, it’s fair to conclude that at least part of His reason was to present a challenge to bechirah. I don’t see why there needs to another reason (applying “Ein Hakadosh Baruch Hu ba bitrunya im briyosav” assumes this nisayon to be insurmountable; it clearly isn’t as many are ma’aminim despite the appearance of the world, and I doubt this is a bigger nisayon than the yetzer hora for A”Z).