deathpectation
thanks for constructive insight, I agree with your view.
You are welcome.
Unfortunately, most of the models are after pixel 5 have this default security feature which.
If by default security switch you mean the fact that you can't unlock the bootloader...no, that's not a security switch. The bootloader is always locked - that is a security feature. However, the bootloader can be unlocked as described above. And this was and is possible with almost all Google Pixels - except for those that are locked by the mobile carriers- as it appears to be in your case. Solution see above.
The chance to find a factory new OEM unlocked pixel pro are almost negligible
That's not correct - what source is your conclusion based on? The Pixel devices mentioned here are fully supported for installing GrapheneOS - this also applies to brand new devices.
If you search the forum for good ways to buy a Pixel, you will certainly quickly find recommendations for your geographical region. A safe bank (regarding OEM unlocking) seem to be Google Stores - online or offline.