In the meantime I think there are a couple of possible workarounds for this particular scenario.
1. Before putting the system into production, add -updates to sources.list, run apt update, install the required packages, remove -updates and run apt update again.
2. Install from non point release media (eg. the original 20.04 instead of 20.04.1). Note though that you won't get updates available since the original release, whereas many would be happy to have those and just prevent further updates during production.
In the meantime I think there are a couple of possible workarounds for this particular scenario.
1. Before putting the system into production, add -updates to sources.list, run apt update, install the required packages, remove -updates and run apt update again.
2. Install from non point release media (eg. the original 20.04 instead of 20.04.1). Note though that you won't get updates available since the original release, whereas many would be happy to have those and just prevent further updates during production.