The tests are there because not everybody is as competent and responsible as
you belatedly claim to be. Do you really think that other water users should
have their lives put at risk just on the say-so of some holidaymaker who
claims to be experienced? Of course not.

You point out that having a licence does not guarantee safe behaviour. Of
course it does not - but it helps. A system of driving licences on the road
does not stop people driving drunk, driving too fast etc - but you can be
sure that the carnage would be many times worse if there was no licence
system. Exaclty the same applies to water users. If anything, the system
needs tightening up much more, because as you have already pointed out it is
relatively easy to forge an ICC.

As others have already advised, if you are as competent as you claim, you
will have no problem at all passing the test.