that's not really what's going on, and it's also not a useful truism. "clearance" is the term to describe a void or space between two surfaces, usually opposing. "tolerance" is a measured deviation or allowance from a given specification to account for inaccuracies during manufacturing and the AK-47 (the "AK"), the AKM, and the AK-74 have similar tolerances as the M16.
for example, the AKM has a fairly consistent tolerance of +/- 0.003" or 0.1mm for nearly all parts that are stamped and about half that for milled components. this is about the same as the tolerance for the M16 (which varied from 0.0015" to 0.003" depending on the component, although some major assemblies had stacking issues and were allowed to go up to 0.006" when assembled).
an in-depth comparison has been done to death by many many people, most who know the topic better than i do.
edit: what is true is that the AK and AKM is generally over-gassed, meaning the gas system has more pressure than necessary to drive the action. this helps in overcoming difficulties with temperature or debris, but also harshly drives the long stroke carrier/piston assembly which increases actual and perceived recoil. the M16, using much less recoiling mass and a more finely tuned gas system, does not do this. the M16 instead relies on user-consciousness and a relatively sealed system for reliable function in adverse conditions. even today, a "solution" for reliability problems that some people experience is to purposefully over-gas the AR-15/M16 system, or a derivative thereof (HK416 for example) instead of fine tuning it or the ammunition, or just flat out using a better system like the AR-18. over-gassing is using a bigger hammer. it'll work to drive a brad nail, but it won't be as clean or precise as a nail gun or tack hammer.
