Yes, but reading further into it they argue that the same could be said for exercise and we know exercise has short term effects effects and long term benefits. (transitory effects: elevated metabolic rate, heart rate, hormonal changes, etc that resolve over time).
There's a hump around 2-3 minutes for myself. Once I get past that my skin gradually stops feeling like it's on fire and I can go for 8-10 minutes easy.
First time I went at a sauna/spa place, it was a big deal to watch someone grit their teeth and go into the cold plunge pool, and then step right back out.
I went more recently and there were people just hanging out in it like a hot tub. Granted, it was a group and they were only partially submerged. But they were in there for more than 30 minutes and no one wanted to go into the small plunge pool while they were there.
It wasn't mentioned in the article, but the temperature of the water was 10°C. A 15-minute plunge at that temperature seems a bit long to me. I did daily cold plunges for about 6 months, ranging from 6° to 15°C, and 5 to 15 minutes. The sweet spot for me was that the water had to be colder than 10°C, but the length of the plunge didn't need to be for more than 5 minutes. I'd be curious to know if it improved my blood pressure - perhaps I need to get a blood pressure monitor to track this.
[1] https://www.sciencedirect.com/science/article/pii/S030645652...