About bolts strenth, I remember 30 years ago I had my two young sons breaking bolts held in a vise.

I wanted them to learn where is the reasonable point where they could tighten 1/4, 5/16 and 3/8 inch low grade bolts, and break them. At their age they assumed metal was unbreakable. This helped a lot when they started working on their cars.

About caliper bolts I can say I always re-used the original ones or took used bolts to replace the damaged head due to over torque. I also never had a caliper come loose during my 52 years driving Volvos (since 1967).

But I agree calpers are critical pieces that no one, nor specially a garage want have problem with a client. I see why they tend to over-tighten our wheel nuts, giving us trouble putting the spare wheel.