It's some evil genius market segmentation on behalf of Pyrex management.

This sort of thing subverts the usefulness of trademarks. You buy from a traditionally upright company, but they just bait-and-switch you on the strength of their trademark and you might as well have bought any product labelled as pyrex.

This is why I like the concept of an "origin mark" that links to a full record of the whole supply chain for the product. Companies already have that information, exposing it makes buyers able to make [more] rational decisions and then capitalism can actually work to improve products.

That said, using the same trademark for different products in this way should invalidate the trademark (maybe UK TMA1994 S3 can be used in this way??).