Not sure I see smoke or suspect fire here. The official company response is an unambiguous denial:

“We are aware of the recent false claims suggesting that a Brother firmware update may have restricted the use of third-party ink cartridges. Please be assured that Brother firmware updates do not block the use of third-party ink in our machines.”

“Brother printers do not intentionally degrade print quality based on whether a Brother Genuine or non-genuine ink/ toner cartridge is used.”

As much as I like cheaper toner... every time I've ever bought 3rd party toner or ink it has been seriously sub-par.