In the 90s mate teams could make transfers all year round. Except for a couple of months at the end of the season - I think it was April and May when you couldn't buy, presumably so that teams could focus on the serious business of winning trophies without having their star players nicked! The transfer windows as we know them today came in early 2000s iirc.I think the nervousness comes from not wanting to be dry bummed by fellow PL teams in USA due to lack of playing squad. As long as we have what we need / almost need by the first competitive game in a few weeks it'll be sound.
I don't know about anyone else but growing up I genuinely don't remember teams signing many or any players in the summer whilst you were still in school, all seemed to be when you were on your 6 weeks off. But that could've been because the transfer window never shut. I'm just gonna wait here for everyone to absolutely prove me wrong and provide a raft of players signing in June / July during the 90's...