Should the the timing seal/crankshaft seal of my new 2019 Hyundai Tucson need replacing at the first service?

I don’t think you have anything to worry about, Yash. Oil seals often weep a bit of oil and it’s good to see that the dealership has noticed it and wants to change the seal, rather than ignore it and make it your problem once the car is out of warranty. Speaking of warranty, your car came with six years of factory cover, so even if the seal leaks again in that time, it won’t cost you anything to have it fixed.

As for your other concerns; an oil seal is not a big problem and won’t cause any other damage (unless the oil is pouring out and leaving the engine without sufficient oil (which it isn’t in your case). Changing the seal will have no effect on the rest of the car, the problem will probably never occur again (not in the 10 years you plan to own it, anyway), the seal can be changed simply without opening the engine, and the cause is probably something as simple as a seal with a small manufacturing defect or one that was accidentally `pinched’ during assembly at the Hyundai factory.

Modern cars are incredibly complex machines consisting of thousands of parts. Even the best models from the best makes can have small defects like this one. Don’t sweat it.