all the existing welfare rules still apply, so you should not ignore them in order to try to fulfil this requirement too - it does not over-ride everything else. It states “Whether you keep just a few birds or thousands, from 14 December onwards you will be legally required to keep your birds...
Welfare laws still apply, as do planning regs! If you read the guidance carefully
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/941139/biosecurity-poultry-guide.pdf
you'll see that they recognize there is a balance to be struck in many cases...