Most currency has two units? Dollars an cents, pounds and pennies. People can understand this!
Discussion
No currency has 1 commonly-named unit worth 100 million times the other. If worth100 times, that's reasonable. If worth 100 million times, that's ridiculous.
Which means that noone will really talk about "bitcoins", because evwryone will deal in sats, when we have gone another 10x. A bitcoin will be out of reach for most people. I am sure there are other examples of the currency and the unit having different names.