kwaigonegin
Colonel
That's also an amphibious vehicle. It's no use having nice big doors if they will instantly sink the IFV if opened in water.
Most Chinese APCs and IFVs have nice big double doors, so it's not like they didn't know the benefits of those.
For amphibious IFVs, the biggest risk comes from when the vehicles are swimming ashore, so having doors designed to be useable in the water is more important.
You don't open the doors when your're still very feet wet or semi submerge. Half a swing door would sink it as easily as a full ramp door if opened. I'm sure the designers had reasons to make it so due to some compromises they had to make however fearing water going inside it is not one of them.