That, or all the changes that the UK are bringing in/just come in, many based the on the findings of The MAC (Migration Advisory Committee)?
It was announced years ago that all these would have to come in. The changes to the welfare state and the law to change the definition of "ordinary resident for the NHS" (who can use the NHS bill free), are not unexpected. All part of getting net migration back down to just tens of thousands a year again, as that article states.
The UK even announced in parliament in 2015, that the welfare changes meant that from 2017, Germany, Sweden and France would now give more money in benefits than the UK does.
I'm not convinced it is Brexit alone as the many millions who have used the EEA Regulations to enter the UK, are now trying to stay in the UK. Over 500,000 of these have been granted British citizenship in the last year. There is a massive upsurge in those applying for DCPRs and PRCs (needed to apply for British citizenship) and there is no need to have these if they don't want to apply for citizenship or will never be granted British citizenship because of their crimes.