Good catch, I see your question as valid (something to learn from), therefore expected, just expected that @hank removes that “in reality” /dev/mmcblk0p1 visible partition (related to output from Ubuntu post in this thread),
Anyway, f3probe looks like very helpful tool. Today I’ve used it for the very first time, just happened thanks to your recommendation.
While related output was based on lower F3 probe 7.2 version, probably obsolete if used with 256GB SDXC card. And while: “Without option –destructive, one would see a line “Probe finished, recovering blocks. . . Done” in the previous output to let the user know that f3probe has recovered all blocks in the drive to their original state.” or
“The problem with this approach is that drives are still getting bigger, and counterfeiters may, in the future, be able to profit with fake drives whose real capacity are large enough to fool these partial tests. This problem is not new.” or
“The option –destructive instructs f3probe to disregard the content of the drive to speed up the test.” or
“When a drive is not fake, f3probe writes about half of its size, or 2GB, whichever is smaller.” or
“You should not easily settle down for a fake drive, fight back and get your money back! Doing so will help you and others. If you are still reading this section, you already realized that you own a fake drive, and would like to be able to use it without losing data.”
as author explained here, containing other relevant points related (like f3probe /dev/mmcblk0) to this thread: https://fight-flash-fraud.readthedocs.io/_/downloads/en/stable/pdf/