Needle decompression in theory is very easy. Needle decompression on fit military age males isn't terribly difficult. The farther you get from that, it becomes exponentially more dangerous and less successful........that much has been definitely studied and proven, with up to 2/3 of professional providers misidentifying the site. At my old job we even had a paramedic with over a decade of experience misidentify the site and puncture the heart of the patient.
Needle D in theory isn't hard. In real life, it's not that hard to fuck up, either, and you likely won't get covered by a good Samaritan law for performing a skill that you're not certified by any accredited body to perform. Good Samaritan laws are almost always reserved for those acting within the scope of their training.
I've never seen professional practitioners act/speak as loosely with applying needle thoracentesis as laymen on gun forums do, in particular. The same applies for this thread, where the only people with known real training and experience are basically saying to slow up. There is simply no good reason in suggesting needle decompression for people who are still at the stage of asking what they should have in a med-kit.