What an ill-informed outburst! I've heard 'different gravy' for many years to describe something that's the best of the best. Presumably it derives from another old phrase - "It's all gravy', which metaphorically contrasts yer basically not that tasty meat & potato with the enriched and augmented juices of the meat that give flavour to make a statement something like 'life is good'.
A further evidence that this is an old derivation is that since the 1960s many people have only experienced gravy with factory-made stock (e.g. Oxo) added or, even more hideous, made from a product like Bisto, which is manufactured from ground up Pam Ayres doggerel and accordingly vile and vulgar. No-one could imagine these cordials to be a sign of quality, so it's impressive that the meaning hasn't changed to mean something like 'insipid, adds minimal value' which are remarkably similar to my impressions of Herbie Hancock on the 2 occasions I've seen him play for us.