I think there are more experiments that need to be done before bold conclusions can be “scientifically” determined.
These experiments should be done with darkly colored water so one can track its penetration.
Immerse fully without squeezing.
Then make new foam pieces that are heated in an oven and quickly immersed fully into cold colored water and held for a time.
Then make new foam pieces that are reasonably well sealed with a couple of coats of thick resin. Heat the foam and quickly immerse it fully in cold colored water for a time.
Then make new foam pieces that are reasonably well sealed with a couple of coats of resin. Poke a single hole in one side. Heat the foam and quickly immerse fully in cold colored water for a time.
Lastly,do the same heated tests above, but this time, cycle the heating and cooling processes a few times.
After each test weigh and cut open the foam to compare penetration. This will also indicate the pathways that the water finds to work its way into the foam. Through the beads cores or along the junctions between beads. Or both.
BB