The response re the probes is trying to say it's a wired probe, so putting it into a fermenter doesn't work if the wire interferes with sealing the fermenter. Then they're saying if you can handle having the wire through a hole into the fermenter, those two models are submersible.
That said, even submersible items are not necessarily suitable for placing under pressure, and thermowells are the "right way" of placing a temperature probe in a liquid. (As others said, a sensor covered with insulation on the fermenter exterior is good enough.)