Howdy,
I think Pine is fine for hugel beds. Particularly if it well decomposed. Waiting a few years before incorporating it into a bed is not a bad.
If you are able to split it open that will also increase the rate of decay. Making sure it stays near / partially submerged would also ensure it remains moist
enough to decompose.
There is no harm I can imagine in incorporating the fresh log into the core of a hugel bed, so long as there was enough soil/rotting stuff for plants to take
root in as the log decomposes.
Sepp utilized newly fallen, large diameter spruce in some of beds (after a massive storm hit europe and knocked a lot of the monocultures down). The spruce is not unlike pine in terms of acidity and whatnot, and it seemed to work fine for Sepp.
Here is a
thread about a hugelbed we just constructed this spring that incorporated a lot of pine.
https://permies.com/t/20131/cascadia/Permaculture-Edge-weekend-forest-permaculture