MRG is absolutely right here.
I wouldn't replace coil stops that aren't suffering wear, just because I had the mechanism apart. (This sounds like I'm contradicting my earlier advice that the problem would be overwhelmingly likely to be the coil stops! But if it isn't the coil stops, you don't need to replace them.)
There are a LOT of different things that cause problems with flippers.
When I read the OP's report, I immediately thought ?End of Stroke adjustment?
You know, it's a funny thing. After doing a LOT of pinball repair, I do a lot of little things absentmindedly. I'll pull on this wire, bend a switch blade a little, check the 'feel' of a mechanism... and I don't even notice what I'm doing.
It's quite possible your tech adjusted the End of Stroke a tiny bit when he was looking at the flippers, and that helped. It's also possible that the whole issue was dirty sleeves.
When you noticed that the technician seemed as if he would just put in an all new parts kit rather than attempt repairs... well, that's a pretty good idea. Pinball repairs are very parts intensive. If you don't have the part you aren't going to properly fix the problem a lot of the time. A lot of the time I'll replace quite a few parts when I encounter a flipper problem. It's not a bad idea to buy a full flipper rebuild kit set and throw it in the bottom of the game.
I'm just glad that you got your machine to play better.
As for making it play exactly as if it were new out of the box, making the flippers feel as if they were brand new... Well, I would have done exactly what your technician did, then I'd replace the flipper rubber (surprising what a tiny bit better rubber grip on the ball will do to make your flippers seem powerful!) and I'd polish the playfield.
Then I'd be looking at other things. Last week I had an Addams Family. The problem that got his flipper fixed was the bushing (unusual when it isn't visibly cracked), replacement flipper bats (lower right flipper bat shaft was bent just a tiny amount so it wasn't perfectly straight) and the standard 'plunger-link-crank-arm sleeve stop EOS switch and return spring'. Now, an Addams Family almost always is worn to the point where looking for the exotic failures is probably where you are going to find your issues, but in this case it was the bushing and flipper bat shaft keeping the flipper from it's best performance.
Thanks for reporting back to us on what got your machine fixed!