I have to admit that I've never understood where this urban legend comes from. Glock wasn't even a firearms designer.Glock was thinking out of the box, and created a wildly popular line of pistols.
What he wanted was a government contract for a new military sidearm. To that end he sent out engineers to study what worked best in successful handgun designs and had them incorporate them into what we now know as the Glock 17. There is nothing out of the box about his design...it had all been done before. As already pointed out, the first production polymer framed handgun was the H&K VP-70Z and VP-70M
What Glock was very good at was marketing his design...there it helped that he wasn't a gun person, but a businessman/manufacturer