Do most watches have ports that are designed for thousands of uses? My smart watch sure does. But of all the possible avenues by which its waterproofness might fail, that connector is #1. I'm pretty sure its custom, as the cable has actual pogo pins to connect.
Strictly from a product design and especially hardware design standpoint, I get the resistance to easy replacement of certain parts. Designing for a replaceable battery means designing your seal to withstand at least twice as many battery replacements as the law requires, or you make sure you have enough replacement seals stockpiled to cover the number that will be replaced, or you use a a commodity seal (think an O-ring).
Apple eventually made ~86 million iPhone 8 and 8 plus. Let's say that's representative of any given model of phone. How many millions (billions?) of seals is that? How much does that cost to store? To distribute? How much does that affect the cost of the phone?
I am fully behind right-to-repair. I won't work for companies that have lobbied against it (and as an embedded hardware and firmware guy, that's significant). But there is a measurable, monetary cost to designing things to be repaired. Either we accept that only the richest n% of e.g. phone manufacturers can afford to stay in business, we as the consumer accept lower performance at the same price point, or both.
All of that said, my point regarding connectors with finite cycle lifespans is relevant. These physical devices themselves have a lifespan. What is the point of replacing a battery when the charging port, headphone jack, physical buttons, touch screen, etc are spec'd to fail well before the average battery does? What about if you have the same iPhone 8 soldering problem, where the phone can't actually survive being put in the back pocket of a decently tight pair of pants? How does government regulation regarding batteries reverse the trend of people buying cheap things because they cost less?