That’s an interesting read. Not least because nowhere does it mention spitting being an enforceable offence. Nor here,
https://www.gov.uk/guidance/fixed-penalty-notices-issuing-and-enforcement-by-councils
So much else questionable.
Presumably “the system” is the DVLA database and they’ve accessed it in a way not covered by those guidelines?
Assuming it’s akin to littering then they’ve issued a maximum fine rather than the default.
They’re supposed to give you an opportunity to pick up litter. Why didn’t they ask him to wipe it up?
They’re not supposed to issue FPNs for trivial offences.
They’re not supposed to issue FPNs when there’s no evidence in case of failure to pay.
They have to make enforcement details publicly available, including details of what’s considered an offence. Have they? Who are they issuing fines on behalf of?