I have this case https://www.samsung.com/uk/mobile-accessories/led-view-cover-galaxy-s10-plus/EF-NG975PBEGWW/ on my S10+. I set Settings/Lock screen/Always On Display - turned on. If I leave the case not closed phone keeps me loged in and I can use the phone without typing the password again whenever I want to use the phone. If I close the case and open it I must type the password to use the phone. I was expecting to use the phone without typing the password when I close the case and open it.
Hope I have explained well this time.