you might be right... I find that odd though that you can still find and buy a super cheap CPU that is still used on the OPII but the SMT flash chip that are way more recent than the old flash chip that were in the old sockets wouldn't ?
Old CPUs are everywhere. They were in tons of products over decades. They used to be state of the art but now they are a really cheap way to put some intelligence in a simple product. Your keyboard for example - how much CPU is really required to scan the keyboard? But the job needs doing. They are often licensed by small manufacturers and can be manufactured in old fabs. They are easily cloned. New CPUs using old CPU designs are sometimes made with newish fab technology to achieve a smaller form factor, lower power consumption, and modern packaging.
Flash technology is moving very fast. A given model number has a lifespan of maybe a year. It's not like a LOT of companies will design in a specific flash chip, there is lots of competition. As technology gets denser the price per unit of storage drops a lot. Flash parts are a definite commodity and an upgrade is usually not very much work. The OPII add-on board was probably not a big effort. It could be that the flash part used is much larger than the CPU can address, depending on how it is mapped in. I've seen 4k *bytes* of flash used in a 1 mbit flash chip simply because the smaller chips were either not available or cost more.