Can any clever person help me understand this.

I have an older Denon AVR (European version of the upgraded 5800, 13+ years old).

I an thinking about replacing it with a new Atmos AVR (X7200W) when it is out.
I wanted to test if the basic codes (volume, input selection etc.) of my current AVR would still work. I tried two tests that gave conflicting results.

Test 1 I added to my remote (MX850), the Denon 4311 codes, (their previous top line model), direct form the URC database on the remote code 1324. My current AVR did not respond to basic codes.

Test 2 I used this code set for the current top AVR the 4520
[Link: audioproducts.com.au]

pages 2 to 7, with the Denon make hex code generator, and my current AVR did respond to the basic codes ?

Any idea why this is and if the current basic codes from my AVR would work with a modern AVR ?

Thanks