I think the closest functional harmony explanation that exists is: this a deceptive cadence to a minor iv chord. Working in C min, it would be fairly common to see these sorts of progressions:

`| Cmin | Cmin | C7(♭9,♭5) | Fmin |`

`| Cmin | Cmin | F♯7       | Fmin |`

As you know (and as the two lines above demonstrate), the F♯7 chord is a tritone substitution for C7alt, and the F♯7 chord wants to resolve to Fmin. When I listen to the songs you linked, I find myself waiting for the minor iv chord to appear. The fact that we move back to the minor i chord (Cmin in the example above) instead of the minor iv chord (Fmin) is surprising.

The progression above doesn't have to have a minor tonality. In other words, it may not be a imin-i7alt-ivmin scenario. We could have something like this:

`| Cmin | C7(♭9,♭5) | Fmin | B♭7 | E♭Maj |`

`| Cmin | F♯7       | Fmin | B♭7 | E♭Maj |`

But much of this analysis goes out of the window after the first iteration. As the progression continues to cycle from the imin chord to the ♯IVMaj chord, my expectation for resolution to the ivmin chord is replaced by a sense of shifting tonality. That is, I feel as though the piece is moving between two different tonal centers. The tritone interval is relevant because the likelihood of a Cmin chord and a F♯Maj being functionally related is so low.

But having a major chord quality on the ♯IV chord is important too. Preserved a minor chord quality would maintain a more continuous feel in the song. Sure, the tonal center would shift, but at least it would still sound minor and thus somewhat familiar or continuous. But by changing from a minor chord quality to a major chord quality, there is arguably a bigger shift occurring than if the progression were Cmin to F♯min. The song feels oddly uplifting at the ♯IV chord. This also contributes to the feeling that we're moving between two tonal centers. 

It might seem obvious that the biggest possible change is from Cmin to F♯Maj, but then again it might not. After all, an F♯Maj scale share more tones with a Cmin scale than F♯min shares with Cmin. F♯min is "farther away" from Cmin as key signatures go. But despite this, the change from minor chord to major chord represents a big shift that catches the ear.

The presence of a second, altogether different tonality is emphasized in some of the links. For example, in the last link you shared, we hear this:

`| Amin  | E♭Maj  | Amin  | B♭Maj |`

It's almost like we're hearing a I-V progression in E♭ with an A in the bass. This sort of technique--playing related major chords on top of an unrelated minor chord--is not that uncommon in certain types of avant garde music. The desired effect is one of dissonance, and I think you're finding that this element has made its way into some heavy metal music.