No, they are saying sorry before they actually do anything, but presumptive isn't it? They should say excuse me, then say thank you when you oblige. Sorry is what you should say when an inconvenience has been caused.
When someone wants to get past you, for example in a supermarket, and they say 'Sorry' and then they make their way by. It's ****ing 'EXCUSE ME' you ****. 'Sorry' is what you say when you accidentally knock into me.