"Warp time dilation"?
While temporally wonky and certainly dangerous, isn't one of the the main benefits of warp drives precisely the lack of time dilation? But yeah, of course, people that go on a warp trip knows that it is dangerous and that it could be years until they reach port. But the vast majority of the Imperium probably have no clue that significant time travel is a danger of the warp.
Sure, the vast majority of the Imperium don't know that significant time travel is a danger of the warp. But that's just because the vast majority of the Imperium doesn't know squat about warp travel at all. A ship's crew, on the other hand, will, even if it's only superstition, oral histories etc.
But no, warp travel is not time dilation free - quite the opposite. It's just that the time dilation isn't constant the way it would be with 'regular' (Real World) high speed travel. A ship in the warp will experience time differently than people in the RW - you might live for three weeks in the Warp while 6 months go by in the Imperium, or spend 6 months in the warp while three weeks go by in the RW.
In any case the crew of a long-range warp vessel (one that makes more than 5 light year jumps regularly) accepts that they're unlikely to ever return home (assuming 'home' isn't the ship they are on, which it will be for most of them). A Rogue Trader leaving Scintilla for a trip out to the Koronus Expanse might not return for a decade or more. One leaving for another Segmentum might not return for centuries (if ever). And the crew don't get a say or any warning of which it's going to be. If you agree to work for a RT (as opposed to being press ganged or bought, which most new recruits probably are) then you do so knowing that you're basically signing your life away.