Whilst you may well be right Bernard, it is still only a hypothisis by yourself - and therefore not a certainty.
It has not been proved. By this token, many of my thoughts about glass and various manufacturers would have long been fact, however, rather than start an unfounded rumour (that is without factual evidence) that later might need changing I prefer to keep much of that to myself. Whilst it is good to suggest an idea, I suggest it is still just thought.
The Scots would say, at best, "NOT Proven".