That's not true actually. What some people don't realize is that the bottom of your hand isn't as heat receptive as say the back of your hand. This is because you're grabbing touching things, sliding them over things and while they still feel soft, the back of your hand is 20x softer and way more receptive to heat. This is why they say in a fire or something like that and you're behind a door or if you want to test the heat to use the back of your hand because by the time you feel the heat through the front of your hand you'll already be burned if it's at that point. So it just takes longer to feel warm, doesn't mean it's too hot.
Now on the upside is if it feels HOT then yea it's going to be to hot to the animal. At about 115 is when our brains register that something is to hot, and if you want to verify this go test your water temp then leave your hands under the water. Within 5 seconds you'll pull your hand out unless you have a higher pain tolerance and then you can keep them there and you'll get used to it but when you pull your hands out you'll have a superficial burn which will go away within a few minutes. This is why your skin turns red.
Some people are just more receptive to heat and just because the heat pad feels like it's hardly working means it's doing the job correctly is a broad statement. Put your back of your hand on the pad, if it feels hot then it's too hot, over 100. If it feels slightly warm then you're going to be in the low 90's. Then you have to account for the heat to get up through the substrate which will cause heat loss so while it may be right on spot at the mat it may not be on top of the substrate. This is the reason it's best to have a thermometer and I'd say a infrared temp gun because you can get top temps. Now don't go adjusting your heat pad which my statement on it feeling warm is okay because I'm just using that as an example.