Bit harsh Mike. Not everyone is the same as you. I string for a bunch of rec players (from 3.0 to 4.5) and none of them are having arm issues with poly. It's just about keeping a very close eye on the health of your arm (which is the first question I ask when someone comes to me as a client). If their arm is healthy and they're not playing excessively (or with excessive force), most people have no problems with poly. One guy refuses to cut it out and has played with dead Alu for 2 years without any problem at all. So go figure! I'd love to know the physiological differences that lead some people to have problems whist others remain fine (I suspect it's connected with pace/power levels as my clients tend to be softer hitters and clearly the harmful vibrations are amplified by power).
I wouldn't describe any of my clients as 'pro-wannabes'. It's more that people want a string which will last a long time... and I'm of the opinion that if something is working fine then there's nothing wrong with it.
Having said all of that, I totally agree that it's possible to play high level tennis without poly and technique is paramount. There's no doubt that poly can make it EASIER to play, and DOES enable higher performance...but that 'cheat code' often actually hinders the development of optimum technique. The best players are those that concentrated on technique long before using poly, and thus don't rely on snap-back to produce spin. Those players can switch between any frame with any strings and still achieve unbelievable spin and control. But it takes a huge amount of time and money (not to mention natural ability) to reach that level...and for most of us, we'd rather just play a couple of sessions a week using the cheat code!
I think these days there's a lot more awareness in the tennis industry (even amongst rec level stringers like myself) about arm health and the dangers of poly...so many people are given good advice as soon as any arm problems develop.