Change addresses in old backups

I have a very old wallet backup, from 2011, from bitcoin-qt, I imported it to bitcoin core, but I seem to have only one address, seems that I have no change addresses in the imported data.
Is the current bitcoin core importing wallets partially?
Did bitcoin-qt at 2011 create change addresses in a different way?
I searched, but the info I found mainly relates to much newer versions of wallets than the ones bitcoin-qt used.
Update: using pywallet I managed to get the additional 102 addresses in the wallet, and import them, now I'm doing a rescan.

Only very, very early Bitcoin clients didn't create change addresses automatically.

In 2011, change addresses were automatic, but the address pool was only 100 addresses long (more frequent backups were needed). It was some years later it was increased to 1000 and Hierarchical Deterministic was invented.