That's a new one to me. I've only seen type XHHW conductors in SER cable, but that's irrelevant. I asked if our local inspector would allow this and he said no. His reasoning in my situation was due to the fact that the cable contained paper spacers in it. I didn't put up much of an argument, in fact THWN was a LOT easier to pull anyway.
In your case, I'd think that THWN conductors pretty much sums it up.
There is no "paper" in this cable. After all it IS a wet location wiring method.
I bounced this off the IAEI BB and they say no because U/L doesn't list SE for underground laterals, for that matter THWN is not listed that way either. USE is the only option according to IAEI if you take the White Book as gospel.
OK here is the result for "this" installation. FPL and Lee County have blessed the SER and it is going in the ground tomorrow. I suppose your mileage may vary and it might even here next time. I certainly hope the same inspector (who gave the blessing) shows up for the 305. I am planning on going by to watch and they say I may get a chance to demonstrate my skill at shooting a pipe under a sidewalk. We did have a volunteer who was going to strip off the jacket for the bare copper we won't need but that doesn't look like it will be necessary.