Yes. It's a bit arbitrary why portfolio's in 7.1 can't be password protected yet pages can. A entirely plausible usage-case is you have a body of work, not just a single project, that requires it be hidden.
This ought to be addressed.
I've run into a bit of an issue with hiding individual collection pages in Squarespace 7.1. Normally, by clicking on the settings for a page, you are able to enable or disable that page. However with the new system of "Portfolio Collections" that page disable option does not exist for individual portfolio project pages. I may be mistaken, but as far as I can tell, there is no way to hide these pages (screenshots attached for reference).
This is incredibly troubling as you cannot create drafts of projects, nor if you are duplicating other projects, they will be live with duplicate content until you fix it.
I was thinking possibly that you could move collection pages to other collection pages(in the way you can move products from shop to shop), so in essence you could pre-build the portfolio page on a hidden portfolio collection and move it to the live portfolio collection, but there doesn't seem to be a way to do this either.
Any advice on how I could make hidden pages in the existing Portfolio Collection system or is this just a fault in the new version?
I think the ideal would be to make it possible to move projects among different portfolios. That way:
I can create a portfolio (X) that holds my "template" for projects
I can hide Portfolio X so that it's not visible to the public, only to admins
I can create projects in Portfolio X and then move them to a live portfolio when ready.
As it stands, looks like I'll have to use @mforny 's solution...but I'll have to create a different template in each portfolio.