But exactly how inexperienced was Paul?
Back in those sorts of days, it's highly likely Paul was able to watch his Dad at work - I know Tim and Jonathan Harris watched their dad Michael, from a fairly young age, were able to get into the workspaces and see what was going on
My Dad had a dental workshop/lab in his practice - I went there loads of times as a small child and got to play with all the lab stuff - putty, wax, bunsen burners, mercury (loads of fun having it tickle as it runs around your palms, great fun to bash a drop of it hard and see it scatter into tiny droplets which you can then get to all run back together, I loved playing with it. Not recommended these days.)
Paul was the one with the most artistic talent - something he would have naturally been developing as he grew up - and if he was watching glassmaking - he'd have got a good "feel" for it.
I really don't see why a 20 year old couldn't have been the one with new ideas - and designing at this tender age.