Squarespace has maliciously slowed down the process -
There used to be a way to actively approve the transfer however now the only option is to cancel it and if you want it to proceed you need to wait for 5 days.
I had a domain moved to Squarespace as part of the Google Domains acquisition - because of their poor customer service I started a transfer this morning and I'll need to wait for 5 days.
I also preemptively transferred all of my domains that were still in Google Domains and they've all completed within 30 minutes or less per domain