I wonder if someone would be able to answer this question

No, if you have the disc and content associated with purchasing the game physically, you'll keep those rights as long as you still have and use the disc.

Just to try and get an understanding of the question and what you're looking for, is there a reason why you believed you might loose access to playing a disc version of a game if subscribed to the service?

To define a few things:

Xbox Play Anywhere: Titles that, once purchase, claimed, or in a service you subscribe, can be played on Xbox One and Windows 10, sharing save data and achievement progress.

Xbox Game Pass: Sub lets you play a set of games in the service, and if titles in Game Pass are Play Anywhere, you can play those on Windows 10 as well

Xbox Game Pass for PC: More details are coming later, but it will include a set of games that you can play as part of the service on Windows 10. Not defined if this will be a separate subscription, or part of Xbox Live Ultimate. More details should be
announced today.

Disc based games: as long as the title is installed and the disc is inserted, you'll be able to play that game, regardless of services and subscriptions (save Xbox Live Gold and playing online, you'll need Gold to play online on Console), but owning the
disc that's in a service, either Game Pass or Play Anywhere, does not make it eligible to play on either/or platform, disc will only allow you to play on the platform the purchase was for.

I hope this clarifies and answers what you're looking for.

So what you are saying is whether I purchase these games or sub to Game Pass I will lose all functionality to the disc based versions of these games.

A disc is a disc and only lets you play the disc version of that game on the platform for which you buy it, so if you're buying a physical disc of a PC game, then it's NOT a Windows 10 Play Anywhere title. That designation is for digital purchases only.
So if you're not buying digital, then you don't have to worry about that.

Regardless of that, if you purchased a disc copy and a digital copy, then it's not going to stop you from playing either. You can play the game digitally w/o the disc, or you could take the disc, install it and still play it. It's not going to lock you
out of anything.

you can still playing those games on disc with your console normally. what do you mean with lose functionality?

I thought that if you have games on Xbox One that are on disc & they are play anywhere titles that are only digital on PC & you purchase them on PC which I want to do the use of the disc becomes redundent on Xbox One as you automaticaly unlock the digital
version of those games on Xbox One which I dont want to do as I am more of a lover of physical games. Or can I choose if I want to unlock the digital version of play anywhere titles on Xbox One.