Not true at all. If you have tech skills, you will never run out of job opportunities in the UK
It's easier for him to find a tech job in the UK (there are plenty) than it is to move to the US and get a tech job (for which he'd need to get sponsored by a company).
The biggest difference between US and UK tech isn't job 'quantity', it's job 'quality' (the culture in the US is better imo). But I'm not sure that's OP's priority currently.