That would only apply to domains first registered 2010, not any of the renewals from previous years. It seems that Nominet have added one day onto expiry from 28th to 29th for some reason for all years.
The problem is not with their drop system, that is probably working OK and will drop all domains with an expiry date of 28/2/2012. The "problem" is that there are no domains with an expiry date of 28/2/2012.
eg....
Relevant dates:
Registered on: 28-Feb-2004
Expiry date: 29-Feb-2012
For some reason a while ago they were all set to 29th, so there is nothing as far as I can see that will drop today.