The vehicle is, the munitions are not. HIMARS doesn’t exclusively fire PRsM, it has the useful and much cheaper GMLRS and ER-GMLRS (coming) to employ as well.
But Strikemaster only has NSM which is going to be as expensive as PRsM snd seemingly less useful outside the short-ranged ship killing role.
First up land warfare is not my strength or natural environment (I prefer it when it rocks and rolls), so excuse me wading in on an army topic. If I slip and fall help me up.
I get that a travelling littoral land force may need to defend against a Naval attack such as shore bombardments or hostile amphibious landings. There will not always be a frigate or an aircraft around around to provide this protection. Shore based strike missiles can do this, or at least make it difficult for ships to get close to the shore.
I also get the flexibility and mobility of the HIMARS platform, and the really good range of the developing PrSM family. It is however a ballistic missile and there are weaknesses with this technology (it can be seen a million miles away, especially at sea).
The NSM is a cruise missile, with stealth, manoeuvrability and a good brain. It also has weaknesses, but they are different to the PrSM (it's slow and shorter ranged).
I would have thought there is a place for both, and as we will have 42 HIMARS we don't loose access to PrSM regardless of the selection for the second regiment.
The Navy, I will note, picked the NSM as its anti ship strike weapon for at least the next couple of decades, despite its range. There is however no conversation (that I know of, and I'm not counting SM6/TLAM as a ship strike missile) of integrating PrSM (or an equivalent) to ships despite the better range. So if range is the be all and end all for hitting a ship, the Navy don't seem to have received that memo. And its not as if a large frigate can creep up on an enemy, unnoticed.
I don't see why the Navy have nailed their colours to the NSM mast, and the army would have the opposite view, when both will be operating in the littoral environment.
All that aside, I do believe PrSM would fit in a Mk41 VLS...