At one level it doesn't actually matter does it ?
You apply when you apply, the chances may be lower but there is no siginicant change in your choices since it is out of your hands.
roni has a good point that if you are marginal for this line of work, is it your best choice of career ?
Also, although I believe Andy's model in general, I do not believe that it hold for all courses at all schools.
We have a continued increase in supply of MFE courses, we also see a drop in demand. Easy to see how that might leave a course with more places to fill than it expects. This is increased by the fact that it is rational to apply to multiple courses.
That means that some people are getting a place at somewhere 'higher' than they might have when times were different. They then decline the offer from lower places.
That means the job of making the right number of offers is harder, and inevitably some places will get it wrong by either over-offering, or suddenyl realised that they don't have a full class.