Bikes have had seat and down rubes drilled and tapped for bottle cages or other applications for eons. Assuming one uses good practice, any frame can be safely drilled for a riv-nut, or a bonded thread insert. Tapping the tube directly usually isn't an option because there's not enough wall thickness.

Builders don't have any magic formulas,or secret methods for drilling holes, and you can do the same as them --- if you do it right.