Cost is a good proxy for resources expended. How many devices exactly are thrown away due to damage vs being EOL'd for other reasons, like vanity, or other obsolescence? Repairability does not equal infinite product lifetime, however it does increase material on the BOM and increase the energy required to manufacture the device. Are you sure that those additional increases in material and energy would be offset by a longer observed lifetime of the device?

I mean, I'm not against repairability laws as a matter of consumer protection, but I think it's pure conjecture to jump to the conclusion that it is undoubtably better for the environment.

If you add 10% of material to the average device to gain 5% average lifetime, you're not decreasing waste. I don't think it would add any lifetime personally, as repair and refurbishment shops already know how to open phones that are glued together and there is a huge industry that refurbs these phones already. I doubt screws will increase the average lifetime of the average phone, it'll just increase the number of screws in the landfill.