Again, its because not many players obtained more than one weapon and I can vouch for that statement because yeah...past relic chains were such a grind that it was a huge chore to do multiple ones, even when you try to do many of them at the same time, its just not appealing to do unless you are just THAT BORED in the game.
Whats frustrating about his statement is that I completely agree with him. I also think its bad that not many people complete multiple relics in previous expansions because yeah the grinds were too stupid with a lot of the steps, but the issue is that he went into the far other extreme were the relic grind is too simple, the exact same and boring. I understand the philosophy behind the tomestone idea because you can theoretically get them via multidud avenues but when all you have to do is your daily duty roulettes to get the 3 same materials at the same price in less than a single day the we have a problem.
I really wish they could go back to form and take a page of some of the less grindy steps from the ARR relic chain where you had to do a unique trial, or had a book that required you to run certain content or go on a treasure hunt, or do Fates where you only needed one item per zone (rather than the bullshit 20 of 3 types of memories like in the Shb relic....) Like literally give us SOMETHING different and a tad long lasting rather than making it too boring and quick to get or making it too boring and grindy to get a single one. There has to be a sweet middle and he's not aiming for that.