I don't think that's correct. You have a nicotine tolerance. Hand someone who has never used nicotine a tootle-puffing device with 18 mg freebase liquid in it, have them take one hit, and see what their reaction is. My wife has never used nicotine in any form and did exactly that when I first started vaping -- because my vape smelled so good.
The whole freebase vs. salts thing is quite perplexing. I'm old enough to remember when the ANTZ were all over BT for adding ammonia, which would convert some of the naturally occurring salts in tobacco into the supposedly far more addictive freebase form of nicotine. That said, Juul's nic-salt patent does claim that certain salts produce a faster rise in plasma nic levels than freebase. Are they right? Who knows. I tried a Juul when they first came out, kinda hoping it would reproduce that first cig of the morning feeling. Didn't work, at least not for me.