I am surprised that Mr.Ngo would feel its baffling to understand. Actually HP's name definition is crystal clear.
For Elitebook only: From flagship to lower end should be:
1. HP Elitebook Ultra G1i=Ultra=Flagship, aka: New machine to replace Dragonfly series, G=Generation, 1=specific mk variant, i=Intel. For C-Suites.
2. HP Elitebook X G1i= Executive Premium business machine, X=10=1000 Series, G=Gen, 1=mk1,i=Intel, for higher manager purpose
3. HP Elitebook 8 G1i=800 series, major series of Elitebook, 8=800 High-end
4. HP Elitebook 6 G1i=600 Series.
As for ZBook Ultra G1a=ZBook flagship Generation-mk1-AMD Based.
Very straightforward