All of these sensors are PIR, passive infrared, so they aren’t actually detecting motion. Instead, they are measuring very slight changes in heat as it moves across the field of the lens.
So the reason they say by “pounds” is that they have set the sensor to ignore changes in heat below a certain level. Even though the dog’s resting temperature is higher than a human being’s, the total mass of the dog determines how much heat is being given off. So the smaller the animal, the less total heat. They’re just making an estimate as to how much heat a 30 pound warm blooded animal will give off.
So the three options are those that others have already suggested:
One) choose a sensor with adjustable sensitivity. Some are labeled as “pet immune” but others just have the same adjustment without saying specifically that it’s for pets. For example, I the Fibaro allows for sensitivity adjustments.
https://www.amazon.com/Fibaro-FGMS-001-ZW5-Motion-Multisensor/dp/B01KOGDETI
Two) limit the detection field by partially blocking the lens. you can do this with tape, White out, by attaching a tube over the lens, etc.
Three) change the position of the motion sensor so that it is less likely to detect pets. People who use sensors to turn lights on when humans come into a room sometimes put a tube over the lens and then mount the sensor at adult shoulder height so that the human will pass it on the way into the room. This is a good way to avoid having dogs trigger it, although sometimes cats will still trigger it if they jump into the detection area such as jumping up onto a shelf. 
But unfortunately there’s no way just with software to add sensitivity adjustment to a sensor which does not have that feature.
Of the ones mentioned, the ecolink does have pin settings inside the case, so you can change the setting again later if you want.
The Bosch literally has a little plastic tab covering part of the lens when you get it, which is what is supposed to eliminate false alerts from pets. To increase the sensitivity again you remove the tab, and I’m not sure it can ever be put back.
The Fibaro has a parameter which lets you adjust the sensitivity through configuration from 8 to 255, so it actually gives you the most choices to try. (just make sure you get the Z wave model, as that’s the one that will work with SmartThings. The HomeKit model is not compatible.)
The SmartThings brand doesn’t have any way of adjusting sensitivity, but quite a few people have been successful with the tube and positioning method.
Good luck, let us know what ends up working for you! 