Hi kayla j,
Yes, it would, however it cannot be called HR if it’s under 2.4lb density.
As explained here:
I think you may have misunderstood what you read. HR polyfoam is rarely used in support layers (even polyfoam that is more than 2.4 lbs may not be HR) and it’s not that less than 2.4 lb “shouldn’t” be used in a mattress (you can see the quality/density guidelines I would use in post #4 here ) but that if polyfoam is less than 2.4 lbs then it can’t be HR.
All the best
Mario