Bitcoin Core – Change address of previous backup

I have a very old wallet backup. Bitcoin-qt has been importing this into Bitcoin Core since 2011, but it seems to have only one address. It appears that the imported data does not have a change address.
Is Bitcoin Core currently partially fetching wallets?
Did bitcoin-qt in 2011 generate change addresses in a different way?
I’ve searched, but the information I’ve found mainly relates to wallets that are much newer versions of the ones bitcoin-qt uses.
Update: I imported an additional 102 addresses from the wallet using pywallet. Now it’s rescanning.