That's a consumer data recovery company. They aren't going to use an electron microscope like a nation state, university, or dedicated emulation hacker.
The first two links that you posted don't appear to cover electron microscopy at all. The last appears to show a potential method of attack--which is noted in the link that I posted--but does not seem to show that it's actually been successfully implemented. ("Using SEM operator-free acquisition and standard image processing technique we demonstrate the possible [emphasis added] automating of such technique over a full memory. [...] The technique is a first step [emphasis added] for reverse engineering secure embedded systems.")
Sorry the first link was wrong but the second link was a research paper that showed them doing it.
Just google electron microscope eeprom and you will find hundreds of documents on the procedure. The second link I provided wasn't theoretical. It showed it actually being done.
"demonstrate the possible [emphasis added] automating "
It doesn't say it isn't possible but that they have a possible way of AUTOMATING it. That is instead of someone looking at the image and reading off the bits into bytes, they could take the image and output the data without human intervention.
Your best bet would be to shred the data multiple times (for example with the shred command) and then break the card physically. But shredding takes time so I guess that's not very applicable to your case.
If you have a lighter, you also can try to melt the SD card's insides. That should be impossible to recover.
In any case, you should keep it encrypted all the time and only decrypt it on the fly.
For example with LUKS2.
Shredding might not work the way you expect on a SD card.
The memory cells in a SD Card can only handle a limited amount of write operations. A SD card typically has more cells than needed, so the controller can switch through different cells to improve the overall lifetime of the card. Which means you can't be sure which cells gets rewritten when shredding, so the data you want to be gone, could still be readable.
If you want to secure your data, use strong encryption. Because what you gonna do, if you can't destroy or get rid of the SD card?
So I probably shouldn’t store my MacOS time machine backups on a 250GB microSD card? (It was the only practical thing I had when I started it and I never got around to changing it)
I don't know how MacOS time machine works exactly, but if it constantly writes on the SD card you should consider changing to an external SSD or HDD. The best backup isn't helpful if your backup medium dies.