Nah people interpret that grimorie completely wrong. The warlock fancied his hunter friend and then tried talking to her about warlock-y things. Space magic and space lore and space dragons and the like. The hunter started to show disinterest so the warlock showed off and tried to impress her by saying neither the 'greatest hunter' nor 'brawniest titan' could kill them. The hunter had her interest spiked and 'took the challenge' but we don't know what happened since the Ahamkara were extinct by then!

I do not credit the story for initiating the rivalry, only an example of it that set the stage for the two classes' interactions on a competitive level. This is just an image that comes to mind when I read item flare text like "It was the warlocks who taught hunters to blink..." and "oh yes, a fine cloak, but I have a super condensed super-collider on my arm, can your cloak split quarks?" not exact quotes but these all follow the same competitive tones.

It's also interesting that some titan items throw shade at warlocks like the Wei/Pujari equation and Saint-14 mentioning a pragmatic warlock is a 'rare thing' while certain warlock items seem to praise them and their strength.