V.A. - 2014 - Technical Melodic Death Metal Vol.1 https://www.facebook.com/127487400638447/photos/pb.127487400638447.-2207520000.1453752480./763572253696622/?type=3&theater

There's no point to force "technical melodic death metal" as last.fm tag, yet these bands have some kind of specifity so this concrete definition of a subgenre has some sence.

It's just a tag, not an official genre. If you don't get anything out of it, don't visit. Others looking specifically for these types of bands will have a use for it. It's after all not possible to cross-reference tags (like bands tagged with melodic death metal AND technical death metal). As previously stated, there's a huge difference between for example brutal and melodic technical death metal.

and tech death/thrash metal ?

Tech death is way different from melo tech or brutal tech.

Seriously, can't we just all tag "technical death metal". No need for this shit. Tech brutal death metal, tech melodic death metal.