"powers of two became important, getting someone to make you a 34-bit DRAM would be hard, much less getting a second source as well".

I have several pounds of 9-bit memory. It's 'parity' memory, was fairly common back in the day, and adding another bit just means respinning the simm carrier to add a pad for another chip. Of course, I don't know if anyone is making 1- or 4-bit DRAMS any more, so you might be stuck adding a 8-bit or larger additional chip. Memory is probably cheap enough now if you wanted 34 bits to play with and were somehow tied to larger power-of-two, you could just go to 40 or more bits and do better ECC or more tag space or just call the top 6 'reserved' or something. It's a solvable problem.

Edit: Should have said "x-bit wide memory" everywhere above.

I have built CPUs with 9-bit bytes (because of subtle MPEG details), they made sense at the time and ram with 9-bit bytes was available at a reasonably low premium - that probably wasn't true when the 432 was a thing, RAM was so much more expensive back then.

You could get special sized DRAM made for you, it wouldn't be cheap, getting a second source even more expensive - you'd have to be an Intel, IBM or someone of that size to guarantee large enough volumes to get DRAM manufacturers to bite

If you'll notice, memory is often made on a carrier (e.g. SIMM module). So you don't have to find someone to make you a x9 or x34 or whatever bit wide chip; you find someone to make a carrier out of off the shelf parts with enough chips for your word width (possibly burning some bits). Early 9-bit SIMMs had 2 4-bit wide DRAMS and 1 1-bit wide DRAM. Just need a memory controller that makes sense of it.

(I design memory controllers ....) you can sort of do that depending on where your byte boundaries are (and whether your architecture needs to be able to do single byte writes to memory) - more though I was trying to point out that historically just 'burning some bits' was not something you could practically do cost wise (it's why we built a 9/72/81-bit CPU in the 90s rather than a 16/125/128 one - the system cost of effectively doubling the memory size would not have made sense)

These days (and actually in those days too) memory isn't really the size of the memory bus, often it's a power of two multiple - those 9-bit RAMBUS drams we were using really moved data on both edges of a faster clock - our basic memory transfer unit was 8 clock edges x 9 == 72 bits per core clock - as a designer with even 1 DRAM out there that's the minimal amount you can deal with and you'd best design to make the most of it

My point was there was more than one way of solving the problem (economically optimized or not), and having custom width memory silicon wasn't the only answer. But sure, if you move the goalpost around enough you get to be right.