I thought the seal was achieved at the very base of the male fitting when it bottoms out. Poor choice of words, not bottomed out in the way that a unified burst disk bottoms out and seals against the bottom. I mean bottomed in the sense that the tapers allow no further engagement.Some of the more detailed manufacturer recommendations say to take care not to apply PTFE tape to the first 2 threads. I presumed that was so it does not contaminate that critical area. When taking apart tapered fittings, I've noticed the very end of the male fitting often has some slight deformation to the thread profile which I why I thought that is where the critical sealing point was achieved...and why they said avoid applying tape to that area. However after reading some more, it seems that recommendation has more to do with preventing tape from breaking away from the end and contaminating the system (e.g. getting stuck in an orifice or valve seat). The subject of sealant vs lubricant is so contentious that I'm having difficulty finding an authoritative source.