When those first 20 addresses are used, Electrum generates the next batch of 20 addresses, and so on.
This is not true. It's not that electrum generates new addresses after all first 20 addresses are used.
Electrum generates the 21st address once you use the first address, the 22nd address, once you use the second address and so on.
Yes, you are correct. My bad, I didn't actually count them. I just went with what I remembered, and I was pretty sure that electrum shows (generates) addresses in batches of 20. Well, either I stumbled upon an ancient version of Electrum, or I just had a classic case of "memory corrupt" here.