The long push action come hereded from original Android base, if you block the screen you will not can to change order or some actions on it, but you will need to have the option of come back to normal use and conditions.
Inside each program, programmer can change the long press action for other things but not in the default system, with OneUI or not. In a computer a click is a click and two are two and right click are options, it is the same and may be a order establish by all and for all, that is an standard method for to have a lineal use between us and all devices in the word.
I prefer to have this option than not to have it., and to lose Widgets, clock, weather, access, info...as other manufacturer or devices without options in Main Screen Long Press 
@st_3 I appreciate the information given, and I am sure that some official Samsung moderator will take note of your requirement.
I was going to advise you now the use of a launcher as you said if you were so interested in this option, but seeing the arrival of Android Q and the incorporation of ONEUI 2.0, it could be possible this addition if it looks correct and adequate for this purpose and makes us arrive with Your active statement and service.
Greetings and very grateful for your cordial treatment to this Spanish stranger 
