I'm certain that is because the "normal" use of the product is to create a facsimile of glass. If this material is poured into a mold and allowed to set for an excessive period, it becomes brittle like glass. For our purposes, we would be "molding" it into the vat and would not demold it until it was time to replace it.

In the interim, I recall where I saw the original reference. It is on the "official" FSL mailing list/forum, but there's no encouraging information for the US users there either.