Unexplained balance changes following Babylon upgrade

Following the Babylon upgrade, it seems that some previously empty (aka 0 balance) tz1 accounts got an extra mutez if they previously originated a KT1 account.

For example, tz1VWmnscfeLbGTxn9nureNtjoW344Gr29Mm had an empty balance prior to the Babylon upgrade, but, without any apparent explanation apart from the Babylon upgrade, had its balance changed to 0.000001ꜩ. This breaks any software tracking balances by summing up credits & debits obtained by exporting node data.

At level 655,359 querying this account's balance results in a proto.004-Pt24m4xi.context.storage_error as the account doesn't exist anymore.

At level 655,360 querying this account's balance results in a balance of 0.000001ꜩ despite there being no operation affecting this account in that block.

I couldn't find any explanation around this change in the details of the Babylon upgrade.

Is this an expected behaviour? If so, how is it possible to audit which accounts have had an extra mutez credited to them?