Of course they are going to say that! They will also tell you it's only good for 28 days after puncture, but many work out of a bottle for 2-3 months.
I have to think it's like anything else... The pharmacy and Drs will tell you to toss meds after 1 year, but I've taken things that expired 20 years ago. They aren't as potent, but were fine.
There's certainly more concern/fear/caution placed on anything injectable, but I have to think that the exp date is set as a precaution in case it's not stored properly. I can't imagine it being a problem going 2-3 months past exp if stored in a dark environment at the right temps. If anything, storing at the lowest recommended temp would allow for longer life, as higher temps, to a point, are where bacteria grows best.
I'm not a chemist, so I can't say with 100% certainty, and better safe than sorry, but if the exp date was 2-3 months ago, I've stored it properly, and there's no visible sign of contamination, I'll probably use it.. esp if it becomes impossible to find!