Showing people photos of these parts/prices doesn't indicate there is an issue with breakage. It only indicates they carried the spares.
I've heard stories about troopers getting warned in the field not to strip down their rifles to the minor components. I've never gone through any military's basic training program, so don't have first hand knowledge as to how far they were ever allowed to strip the bolt down, in the field or in the clean up area later.
It would be extremely easy to lose parts, such as the "V" springs, screw, and even the extractor itself under field conditions, if they were allowed to be stripped to the bone.
A newbie or even most shooters, will never attempt to strip a rifle bolt to it's component parts for cleaning and inspection.
Mostly because they don't know how, don't have the tools, or run it as is because it still works.
Mechanical things break. I've had Lee Enfield parts break in the field, because of wear, manufacturing faults, or something loose, that should have been tight.
I personally don't see any issues with single loading a Lee Enfield. I've seen hundreds of them single loaded during DCRA matches with thousands of repeats and no issues. Mind you, some of us carried spares of the components we suspected or "heard" may give us trouble, and the screw/V spring/extractor were in the tins. Mostly we carried sight components.
