Either ram upgrades are still easy to accomplish -OR- 'dodgy hardware resellers' will no longer be able to continue installing bad ram. You cannot have both.
RAM upgrades on a RPi are REALLY hard. You need to have certain hardware and skills to do it. The people who can do it, can also make a killing "upgrading" RAM by using cheap low-quality RAM and selling the new Pi as a more expensive one. The price difference is about $260 from RPi 5 with 1GB to one with 16GB. ($45 for 1GB, $305 for 16GB). If you come across a supply of cheap 16GB units for say, $100 each, you can make a healthy profit selling RPis for $305 that you paid only $145 for. That's $160 in profit and if you have all the equipment to do so, likely takes well under 15 minutes each to do.
The people will the skills to do this easily are also the ones who can acquire everything cheaply - China, for example, would have all the necessary equipment to make it.
You can also get "no warranty" RPis officially - they're the "industrial" model and are not for retail sale. (Many pieces of hardware use RPis internally for their controllers because it saves having to deal with SoC manufacturers and such to design the hardware when it's readily available). That's usually how those factories can get a ready supply of RPis for cheap - an industrial RPi 5 1GB would likely be under $40 or so in quantity.
And now you're counterfeiting Pis.
The FSF is right to criticize RPi for this, because it goes against their principles, but the FSF also has to realize that counterfeit hardware is a real thing, and an RPi with swapped memory not officially made by RPi is a counterfeit. It's one of the annoyances of real life - counterfeits are a real thing and countermeasures to that usually end up taking rights away. I mean, I'm sure all the pro Right to Repair folks would be glad if their names were put on counterfeit stuff, right? Perhaps someone selling cheap batteries with the iFixit logo. The FSF is harder to counter since their products are purely software, but I'm sure they've been burned before when they buy a product only to realize that the new revision was incompatible.