Well, that's not how I used it, nor am I ever planning to. I just bought the same strength nicotine level and added a squirt to my tank as needed.
I can't even imagine using enough "WTA wholesale" for my mixes and to be able to afford WTA. I will say the way I used it worked out fine, and while I don't know how much "WTA" percentage is in all "wholesale" WTA, nor do I need to know, but apparently I need a lot less than 5% to find some benefit.
I can understand using WTA "wholsale" in place of base; I also understand that if I were to do it that way, I would very rapidly grow poorer than if I were actually smoking.
Heck, my last two liters of 100 mg/ml nic, I didn't even buy nic salts, as I am looking to stock fast, then forget about it. I figure if I can't handle freebase nicotine by the time I get to "that part" of my stash (likely several years from now) then I can convert it to nic salts myself.
So, while WTA makers may "feel" it best to DIY just using WTA, there is no way on planet earth that such an action will be undertaken, at least by me. Maybe if it didn't work well the way I've already use it.
With that said, I think manufacturers may well know how to get the "best result" for WTA by their recommendations, but I seem to do fine without that "best" result, so I won't be changing my method. I can also see manufacturers having a "vested interest" in having end users "DIY" with it, as it's probably a fairly expensive way to use WTA. I will say, for me, a small amount of WTA seems to go a long way, so I won't every be following the recommendations, I don't think. Etc.
Anna