It suits my opinion but it is also all true. By "locking out the top spots" I think it's fair to assume that relegated PL sides reserve 3 of the top 6 spots year after year. You only need to look at recent league tables to show this.
I may have my timelines wrong, but wasn't Rosenior sacked by Derby after he had 1 transfer window whilst under an embargo?
21/22 - Derby relegated under Rooney with assistant Rosenior.
June 2022 - Rooney leaves. Rosenior appointed. Transfer embargo etc. They had only 5 senior players under contract.
September 2022 - he's sacked for Paul Warne.
This was the league table when he was sacked.
View attachment 15316
So he got a transfer window with an embargo and 9 games, despite having them in 7th.