Isn't Peercoin PoW2? They have PoW and PoS that you have mentioned in this article.
In Peercoin you sign a block with EITHER PoW OR PoS. in PoW2 you sign with PoW AND PoS. That's a huge difference for security reasons. Malcolm discusses this detailed in the Whitepaper.
Edit:
Find the Whitepaper here:
https://guldenpagina.nl/wp-content/uploads/2017/07/tmp_25790-Gulden_PoW22819007230.pdfRelevant paragraph:
3.4. Combined PoS/PoW
Some coins like Peercoin combine PoS and PoW the theory being that
this makes the coin twice as secure. However, in reality, this doesnt hold true,
the problem is that the PoW and PoS miners are competing with each other
to generate blocks. This, in turn, means more orphans and fewer profits for
miners, which means reduced hash rate. This at best means the gains are much
less than expected and at worst means that it actually makes the security worse.
If multiple PoS blocks in a row is a common sight then only PoS is required to
perform an attack, and vice-versa if multiple PoW blocks in a row is a common
sight then only PoW is required to perform an attack. In short instead of being
as strong as both; it is instead only as strong as the weakest of the two, thus
opening the coin up to more attacks and not less.