Continuing this in another topic because I feel it is important to the safety of anyone who thinks this.
Neither of these statements are correct. Everywhere I just looked online says to place the probe just as I have. As someone that has UTH with the probes between the enclosures and them, I can tell you there is no way they could damage the mat.
If this wasn’t a burrowing species then I would believe you, but that is not the case with sand boas. If it is in the enclosure, he can urinate on it. It just depends on when.
What does everyone else think of UTH thermostat probe placement? There are just too many things that could go wrong for me to ever risk putting them inside the enclosure. On top of the first page on google when I ask this all having results that support placing it between the mat and the enclosure, and not inside the enclosure.