The biggest problem for me in this regard isn't "Is it in previous fluff?" it's "Is it needed on a tactical level?" Fundamentally it's a battlefield we're talking about here and despite all the technological regression going on in the Imperium, it's noted several times throughout the fluff (such as the aforementioned Land Raider Crusader and the MK IV Razorback) that provided it works, you can continue to use it in battle. This rule applies to new tech such as the Storm Raven (smaller more nimble flying transport than the Thunderhawk) and the Dreadknight (though the Dreadknight went against the previously awesome fluff of GK being able to fight Greater Daemons in units DoW style, which I really liked) because you need a big mech to fight Greater Daemons 1v1.
For the Storm Talon however.... No, I can't see a tactical reason for the marines to suddenly start using a vertibird that lacks the firepower of a Storm Raven. The Escort stuff seems silly to me, as Storm Ravens/Eagles and Thunderhawks are powerful and heavily armoured flyers and the need for large numbers of smaller, lightly armoured ships to fly along side them isn't there. They go as fast as the Storm Talon in the game, and don't have the same versatility as a Land Speeder STC.
On a side note, I think all the Space Marine Chapters should have access to the Storm Raven now, especially with the introduction of allies. They are no longer secret or sacred tech, they are being used alongside Ultramarines, Space Wolves and Dark Angels and I doubt that the smurfs, pups or angels would scoff at that level of firepower.
Forgeworld does a very good job of introducing new units in the Imperial Armour books, but then it has the opportunity to really hammer the fluff home there. GW doesn't seem to take the time to do so in White Dwarf or even some codexes sometimes...
I don't think people argue much about the Xenos getting access to new tech, but this almost always with good reason. The Cron's direly needed an update and didn't have enough stuff anyway. Dark Eldar are much the same. Orks can make virtually anything out of anything. Tyranids evolve and create new units to fight new threats. The Tau are still expanding and developing new weapons. Perhaps the only race where it wouldn't make sense for them to get new tech is the Eldar, but they will likely get a flyer soon and we'll see what GW says then.
If things are invented in the Imperium, there needs to be a reason. The Storm Talon does not have a good reason for being there at the moment, just seems like a good way to lose a few gene-seeds in air combat. The Storm Raven on the other hand is a potential battle changer and a good addition in my view, however OP some may have seen it in 5th Ed.