Presumably the research didn't include those I see on almost every bus
journey who signal the bus too late (either with a V sign or an angry
fist) as it sails straight pass compulsory bus stops where people
obviously *were* waiting to board.

In such situations the driver is not conforming to the policy.

It is common for the 410 not to stop at East Croydon northbound in the
evening peak (and to a lesser extent at other locations at other times of
day) despite there being waiting passengers, presumably because the driver
believes the bus is full (although the waiting passengers can often see that
actually it isn't, it is just crowded at the front). Once wonders what the
policy is in that instance.

I always hail buses and ring the bell if no one else has. However this is
because I've long since lost confidence that drivers would actually stop at
compulsory stops otherwise. I know I am by no means alone in doing this.
It seems to me that to some extent TfL have changed the regulations to match
the behaviour of passengers who were responding to the failure to adhere to
the old regulations.

I think it is actually perfectly reasonable to have just one type of bus
stop and to request passengers indicate to the driver that they wish to
board or alight. It would be a courtesy to their passengers to advise them
what they policy now is, especially as those who are most familiar with the
concept of compulsory and request stops are likely to have been using the
bus services for the longest time.