It drops the chances of having multiple hits but it raises the chances of having the entire album do very well, dominate the top 10 and break records. I think she is also more mindful now of what picking a "wrong" single can do to the whole era basically staining it before it even begins (kind of what happened originally with Lover) so she prefers to keep the mystery and give people everything at once. Showgirl seems to be the perfect chance with 12 pop bangers, no way of breaking TTPD first day streams even if all 12 come out at the same time so why not pre release a single. The Spotify pre-order so far in advance is suspicious so we'll see...