The Altair 8800 came out in January 1975; Gates and Allen's Altair BASIC, the first microcomputer BASIC, came out "shortly thereafter" and EWD498 was written in June 1975. That's hardly long enough for an explosion. Again, Dijkstra probably had never even heard of either when he penned his missive and it's clear that his opinion of BASIC was well formed even before 1975.