There was a whole thread about that some months back, I recall the conclusion was that the placarding and wording wasn't consistent between models. There are plenty of tall stories, but again, I believe the conclusion is in the use of the word 'avoid', rather than prohibited - if control reversals occured, I think the wording might be rather stronger! As for nosewheels, if you're half competant to pilot the thing, landing on the mains isn't hard, even with 40degree barndoors.
In a glider you're also pushed towards a crab by long wings and low ground clearance - landing on a wingtip is not advised. Powered I usually fly a crab right into the flare, push straight with the rudder, and drop the windward wing as required to maintain the centreline. Not really rocket science. In either case you fly the aeroplane all the way, and you can judge the crosswind by how far off the runway heading you're pointing (reference to trex540) Stabilised approaches are for big jets
In the main, I'm inclined to think whole thing is rather more down to personal preference, perhaps coloured by your handling comfort, and in some cases dictated by the aeroplane (e.g. wheelers, gliders etc)