No. They increased the max "canvas" size and increased encoding efficiency. You'd want the file size to be smaller but the file itself to be larger (and consequently more detailed)

It's even more confusing than that; the X is for revision 10, and the L is for long term.

It's an update to the JPEG standard intended to cover expected future uses and capabilities.

In my personal tests of jxl, it manages filesizes 1/9th that of png while remaining visually identical (unless looking VERY closely). It's a massive improvement over jpeg and honestly a replacement for png in most cases.

Like I'm saying 8MB for a 8000x6000 file at max quality (estimating from memory)