convex glass - is it a problem?

having been told my lovely SM120 MF is fundamentally flawed, in that it has a slightly covex glass, this got me wondering about the issue a little more deeply.on first thought, it might seem something of a design flaw to have the glass exposed to knocks. but being flat only reduces this exposure rather than eliminating it. also, for a dive watch, convex glass has the advantage of being able to withstand higher pressures for a given glass thinckness. then i realised that it's far cheaper to ge