It’s not strange, it’s because the Marketplace topic is limited to versions [4.2.0;4.2.99). I don’t know what the rationale behind having such a small “window” is, the likelihood of it breaking in a minor version is probably quite slim.
The way it is now, it won’t show up until @hww3 has either edited the topic or created a new one meant for 4.3.0. This probably explains why it “disappears during upgrade” too - OH is probably trying to reinstall the Marketplace add-ons, but can’t find one in this case.