Drawing an ethical line thru a gray area is generally not straightforward. Often it is not possible to find a unique best place to draw it, and sometimes we should treat certain areas as in-betweens.
However, another network card with exactly the same chips and the same firmware, but a different model number, may get firmware updates from the vendor. That would _not_ qualify as ROM in your definition, at least as I understand it. The technical side of the ROM equivalence question does not allow for such distinctions.
This is a gray area. I think we can treat it as barely acceptable if we do not install firmware upgrades. But only barely, so we should move to free firmware if possible.
Firmware blobs which are loaded into devices, but where the blob never changes even for different versions of the driver, would be tolerable according to your definition (please correct me if I'm wrong).
If "loaded into devices" means "loaded by your CPU from your disk", that is never acceptable, because (1) the non-free software is in your file system and (2) you (always) do install it into the device.
As I explained above, free software politics based on "ROM equivalence" in the firmware category do not make sense from a technical point of view.
I think it does make sense, when interpreted as described above.
Please note that any laptop where the manufacturer refuses to provide BIOS updates would be tolerable according to you because "memory is physically writable, but is never updated once users get the product".
Even if the manufacturer does offer BIOS updates, I think we can treat it as barely acceptable if we do not install them. But only barely, so we should move to free BIOS if possible.