Asklemmy

First off, I'm not the arbiter of what does and doesn't belong to a certain genre. That's, to a certain extent, subjective and people don't always agree. However, there usually is at least some consensus in the community, otherwise the genre names would be useless.

That said, I personally wouldn't call this melodic death metal either. Most of the song is just clean singing and clean guitars, both of which are sometimes used in melodeath, but they're not a defining aspect of it. And even the parts with harsh vocals and distorted guitars are missing the riffs that are typical for the genre. It's closer to a progressive death metal or groove metal sound similar to Gojira or Opeth.

Overall Jinjer are also definitely not a melodeath band, they're metalcore, which is often seen as a subgenre of hardcore, not metal, although there are bands that are more on the metal side.

As I said, I'm not the genre police, this is just my opinion. But I think (sub)genre definitions are useful when talking about music and if we start using them too loosely, they lose their meaning and as a result, their utility.