Version 0.99.108-beta on Monterey
CC @saul for spotting this
The Preferences option for new window behaviour was reported to not override opening of existing tabs at startup. Can confirm this behaviour:
I suggest there's a new setting required here - the "New Window" option works fine and opens notes (or whatever) when you pick that option and open a new window from the file menu. The issue here is an unexpected user behaviour (last session's tabs are restored without a new window being "opened").
A separate tickbox option could be - "Restore previous tabs at startup" or similar, as new window behaviour sits independent of restoring tabs - you can have "restore tabs" both on and off, while having the start page set as Notes (or blank).