The tap is making the hole 'bigger' so your male part can go deeper.
Try to stay on topic here.
By using the die you are just adding more full threads at the top of the taper thats are above the engagement.
whereas the tap is carving away metal at the opening so that more of the taper will go...
https://www.oasisngv.com/vdb/document/1179
every thing you ever wanted to know.
Bobmo
USE TEFLON TAPE, and only a couple of wraps.
The good news is that if the fitting leaks you can tighten it a little more and it will stop
Bobmo