Those operations apparently do a lousy job making their presence known.
Unfortunately, yeah, the dive industry around the GBR - certainly the day boat part of it that you will find widely promoting itself on the internet - is very heavily focused around the backpacker and overseas holidaymaker market - and this applies not only to customers but also to staff. Their expected average 'certified diver' customer has either very recently completed an intro level course, or, dives very infrequently, and is fitting "a dive on the GBR" in to a mostly non-diving holiday. Many of the staff too will be backpackers, and may even be
paying to be there as part of a "become a scuba instructor" package. It wouldn't be particularly surprising if you had more dives than the entire rest of the boat put together - I'm far from the most experienced diver and I've certainly experienced that; I'd hazard that 20 certified divers out of 100 might be an above-average proportion for a GBR day boat.
GBR Liveaboards will attract more people who are on a 'dive holiday' as opposed to 'holidaymakers fitting in a day or two's diving', and likely have more experienced staff, though it is still quite possible that some/many of the staff have no experience outside QLD. Some of the liveaboards occasionally run specific exploratory, or tech, or rebreather weeks, but those won't be publicised in the same way - local divers might be more likely to book on those, or smaller, semi private or private boats that don't promote themselves to the tourist market.
Also consider that Far North Queensland has a population of about a quarter of a million, in about a quarter of a million square kilometres - a similar size to Texas with one-hundredth of the population - so there really aren't that many locals to drive a 'regular local diver' scene of any size. The further south and away from the tropics you go, the more you get away from this heavily tourist-driven market - in Sydney, and even more so in Melbourne, a long hose / BPW / drysuit won't attract much attention at all.
A few years ago, a small group of us went on Spirit of Freedom, one of the most up-market GBR liveaboards (and excellent, by the way), around Easter time. We all had BPW / long hose configs (the only setups like this on board), and some of us took drysuits. At the start of the trip, there were some raised eyebrows and good-humoured ribbing from the staff; by the end of a grey, windy and rainy week several of them were fingering the drysuits and asking "how much did you say these were again...?"
Cheers,
Huw