I had the same question this morning, and I just performed a quick check. It appears that a number of recent updates are related to the MOSFET model, particularly bug fixes or improvements to the BSIM3 model, as indicated in the revision history.
This option can be found in NGspice and Hspice. Referring to the NGspice user’s manual and conducting a quick verification test, it appears to be a scaling factor for geometric element parameters. It is likely relevant to microelectronic and IC design areas.
Here is a simple test I just performed.
