In systems where memory speed are mismatched, the system runs at the slowest module’s speed. So literally making the soldered, faster memory slower. Why even have soldered memory at that point?

Signal integrity is a real issue with dimm modules. It’s the same reason you don’t see modular VRAM on GPUs. If the ram needs to behave like VRAM, it needs to run at VRAM speeds.

Which is why it’s based that it wasn’t promoted

Why do you think that? I have seen and heard the use of the word “penultimate” as a literary device to praise something very good. It’s not even that big of a stretch. I’m sorry people only ever use words to mean exactly how they are defined in the dictionary when around you. Also, words are meaningless without the people who use them. Why don’t you try correcting people less and instead, when you think someone is using words incorrectly, try to understand in what way they could be correct.

In this case penultimate is used to describe something that is nearly perfect. As if to say, there is little room for improvement.