first, and foremost as a service tech, pay very close attention to exactly what his job description is, from any given parts list, is exactly what is allowed to be replaced on any given machine....nothing more.....
if his past experience showed just cause that adding a bit of grease would temporarily solve the issue, he may go ahead and do that, but if that same sort of fix, caused more damage, who is responsible?....at that point he should stay within guide lines of what the manufacturer recommends....
the only time he would venture past this is if there were updated tech sheets to inform of problems in the field, and there were optional fixes...
don't confuse something you discovered yourself at home with what an actual professional would do.....even your fix is temporary, doubt your fix will alleviate all issues for the life of the machine...that grease will wear away, and your back to square one....we all have improvised on fixes, wondering why the manufacturer didn't see an issue to this....but in all reality, that noise didn't stop the machine from functioning...and it may have lasted many years without issue...just an annoying noise...
some machines do have some sort of metal grommet on the plastic side, some don't...some even coat the spring for reduction in noise....as in this case, I would have slid a piece of rubber hose over the spring hook, as an added measure for noise, but even as shown in the pic, that hook end takes a lot of wear, its at a stress area, some parts will wear out sooner than others...
some springs 'hum' from vibrations...taking the cotton from your aspirin bottle and stuff inside will absorb the vibrations...now in thinking, what service tech has a bottle of aspirin in his truck?....any given one who has to deal with certain PITA customers who are never happy!