Page Header Code Injection Strange Behavior

I'm fairly technical but *NEW* to Squarespaces.     

Seeing some strange behavior with Squarespace's Page Header Code Injection feature....

First I created a site using the Version 7.0 - Brine family (Hyde template).

One of the template pages is a welcome page containing a handful of sections.   Both the  Welcome container page *and* the sections have as part of their settings a advanced tab with a "Page Header Code Injection" field.     However, while logged in as a "Contributor",  I can clearly see using the browser inspect feature that adding code in the sections does nothing.   Is this the supposed to be the case?    I suppose it makes sense if the injection is just done at the "page" level given the field is called a "Page Header Code Injection".   It's just weird that the Squarespace UI would offer the field for the sections if it does nothing.  At least the field works fine at the page level (or was...see next paragraph).  Also, I thought I read somewhere that this was expected behavior as well but started to second guess this when I encountered the issue below so wanted confirm.

Re: this other issue. .. After getting my site looking the way I wanted, I tried testing it outside of the view I get while in contributor mode by setting it to private with a password.    When I viewed the site this way that custom code I placed in just the ONE page and worked great in the contributor view is in the private/password view now getting injected on ALL pages!!!   

Is this expected?   Shouldn't code I add to the Page Header Code Injection Field for a single page ONLY get injected on that ONE page???   

And shouldn't the contributor view match the protected/password and published view?  Clearly it doesn't but shouldn't it?

Thanks!