Well, possibly.
My understanding is that in recent years those altitude estimates have come from Rocksim, but I have no idea what assumptions about surface finish (and launch site altitude) are used.
Since I fly an altimeter in just about everything I fly except saucer types I know that some recent releases don’t even come close to the claimed performace. I think it might be possible to get a Blue Sapphire up to 1200 feet - on a Q-Jet D16.
The Super Mars Snooper and the Super Orbital Transport don’t come close either. In the case of the latter, it’s fine, as the glider works really well and getting it back from twice as high as as the stack really goes on a D12 would be “interesting“, and seeing the whole flight easily is a good thing with that model.
With the So Long, it will likely be out of sight (but hopefully not out of site) even so. When I get one, it will have an Eggfinder in it when it’s flown F15 to F15, which I sincerely hope to be able to do.