I work with T-Mobile and Samsung (not for them) and I have been a cellphone enthusiast since 2004.
All modern glass screens have an Oleophobic Coating (oleo; oils) that can wear off by natural wear and tear. Solvents (isopropyl alcohol is an example) will dissolve it.
In the pictures provided are my own Samsung Galaxy S24 Ultra that I had used the formula that was the highest recommended. It is bonded Al²0³ (Corundum/Sapphire Glass) and the application can take 45-120 minutes.
You can also purchase your own kit if you would like to try to apply it yourself. Please email me to set up an appointment. Thank you!