Seems like this increases the attractiveness of physical gold relative to bitcoin as a reserve asset, particularly for institutions.
I'm not familiar with this, but I think that you're correct.
How much of an impact do you think this will this have for institutional interest in Bitcoin going forward?
No impact at all. This will impact only those who use certain reserve assets only because they're required by the law.
Bitcoin is for those more open minded and with appetite for a bit of risk too, who want a reserve asset they can have gains from and can easily HODL.
Banks' interest towards Bitcoin was only to get/keep their customers, they will keep using gold as reserve asset.
Corporations on the other hand, will be diversified in basically everything, from gold to stocks and from bonds to Bitcoin. They afford a certain degree of risk and their "expansion" in the crypto markets won't be hindered by re-classification of (the same old) gold.