And YOUR expertise is?
Please explain how the sub gets through spots a person barely could, per many sources. Are those sources wrong? Was there more than one route out?
Ultimately, it doesn’t sound like a good idea. The fins or whatever on the capsule could get snagged and they have no feeling to guide them, unlike the extremities of a human. A human clambered into the cave through the narrows, and could and did clamber back.