This frog-tie self-bondage tutorial was posted by MadJack in the Self-Bondage art forum thread. Looks at steps #4 and #6. If the wrist straps are wide and hard enough, and properly measured, I think it’s possible to make this method inescapable (provided you can get in “one-handed”).
However, if the wrist straps are not secured to the sides thigh-ankles ones, they can be pulled upwards and towards the center, so you can use the other hand to undo the strap.
Very interesting idea, but needs testing.