You're right; also, apparently, Gibson said he hadn't seen
Tron as late as March 1983, and he finished a draft of
Neuromancer before that August
https://www.bookbrunch.co.uk/page/free-article/neuromancer-t... . (Though this also confirms that he
had seen
Tron stills in mid-1982, though that's still well after both "Burning Chrome" and the
Jacked In outline (both 1981)). OTOH the similarities to
Blade Runner have never really been hard to explain: if you cross film noir and hard-boiled with New Hollywood and '70s malaise fiction then it's natural to end up with something a bit like
Blade Runner and so also
Neuromancer, while on the other hand there are of course huge differences between the two as well.