The fact many (note: not all) of those crossing via this means are intercepted and processed through an administrative process does not make it controlled migration.
There is a process in place to deport illegal immigrants and thousands are forcibly returned every year.
About 3000 were forcibly returned between June 2020 and June 2021, although the vast majority of those (2,809) are people convicted of a crime. Few non-criminals are forcibly returned to their point of origin once they are in the country, regardless of their immigration status. Three-quarters of people who enter immigration detention after illegally entering the country are released into the population without being returned.
https://www.gov.uk/government/statistics/immigration-statist...
> If anyone who can get in a boat in France can migrate to the UK, that is, by definition, uncontrolled.
So this isn’t true at all. You’ve just demonstrated that your own justification is false.
The proportion of crossings by boat has increased relative to other means (air/lorries) because the technology for detecting undocumented entries via those other means has improved.
All this is easily looked up. The argument that "some people have done this therefore it is uncontrolled" is absurd.