That's not true at all - there is no law in the UK requiring you to have your license on you at all times, you can produce it later at a station without issue.

It also isn't at the officers discretion, it's law. You have 7 days to produce your documentation at a station.

https://www.gov.uk/stopped-by-police-while-driving-your-rights

If you do not have these documents with you, you have 7 days to take them to a police station. You’re breaking the law if you do not show the requested documents within 7 days.

It's a moot point anyway - the police can run your details through to find out if your licensed at the road side.

The only thing that might lead to your vehicle being seized is insurance, if for whatever reason your policy isn't on MID, and you don't have proof of insurance on you then they may seize your vehicle.