Tire shops are supposed to replace the TPMS seals and nut when the sensors are removed to change the tires. The sensors do not necessarily have to be removed, but there is a risk if they are left mounted in the wheel that they will be broken during tire removal. Most shops will remove the nut and drop the sensor into the tire for safe tire removal. Some shops may re-use the original nuts and seals which may result in a slow leak around the valve stem. It would require removing the tire and replacing the seals and nut if that happened.
The TPMS manufacturers state the seals and nut must be replaced if the sensor is removed, so there is no fuzz on that. It is up to the tire shop to do the right thing. By the way, you can buy the nut/seal kits for about $2 from online shops. Local places tend to charge way more than this - as much as $20 for a single tire kit.