And that requires more space than a typical port. In a compact device that is difficult. A flashlight is literally one of the simplest electronic devices there is and bulk is often a plus for comfort.

They can be waterproof but are also non functional until the water is fully cleared from the port.

That kind of waterproofing wears over time (years). It keeps it's resistance, but not a submersible seal. Watches have longer use years than phones on average.

3 Days is great!

That gives me no information. What's the battery size? I've had multiple smartwatches and all their batteries could last a week or a day depending on usage, setup and features.

The point is USB C is noticeably larger than pogo pins for the sake of including a whole bunch of additional pins a smartwatch has zero use for. Larger means less room for other stuff. The ideal state for a smartwatch is having an always-on display and heart rate monitoring, among other things. All watches out there, even the most efficient ones, could use more battery and efficiency than they have. Because all smartwatches are coming up short from their desired usage and are working around their limited battery life.

The idea of making that worse for the sake of having a clearly unfit for purpose connector as opposed to standardizing a connector that actually does the job is really weird. There is no need to have a different charger on every watch, but there certainly isn't a need to sacrifice any functionality or performance at all for the sake of USB C. And not all watches are the same size, so this would impact smaller watches more, which now is limiting what type of watches you can make if you make USB C a standard. And if it's not a standard, then it's not fixing the problem.

And all that's even before you begin to consider that watches are more comfortable to charge when they have a stand to do so, since they're small, light and fiddly, so it's entirely possible for a bulky USB C cable meant for fast charging to be heavier than them or stiff enough to actively move them around. There's a reason watch chargers tend to come with very thin, flexible wires. All you need to fix this problem is a magnetic stand that can hold any watch. Half the USB C cables I own would knock over my watch stand if plugged into my watch or drag my watch across the table.

You can make a watch that charges via USB C and still works. That's not an optimal solution, but you can. But it's not a valid standard because you can't very practically make all watches charge via USB C. Standards need to be standard.