One - these exercises stem from ancient yogi practices and they are very stimulative i.e. kundalini stirring - doing them without also doing calming breath work could potentially overstimulate the body and even cause a burn out.
I'm not sure what you mean by kundalini stirring specifically - I couldn't tell from your phrasing but does that mean something separate from sympathetic activation?
I read and enjoyed Wim Hoff's autobiographical book, and I wholeheartedly agree with what you shared above. There's a lot of benefits to Wim Hoff when properly applied with knowledge and awareness. Any type of process which has the potential to facilitate deep re-patterning of the nervous system, which all techniques that may produce emotional release or spiritual experiences can do, requires a period of down-shifting into a deeper parasympathetic tone to integrate the experience over time. Not doing so can in fact lead to greater dysregulation of the nervous system in the short- and long-term.
Wim Hoff writes a forward in the book
What Doesn't Kill Us, which is about the adaptive capabilities exhibited by hunter-gatherer and other societies of the deeper paleolithic. That's from a Friedrich Nietzsche quote "that which does not kill me makes me stronger." This has permeated modern personal growth and "hustler" culture to the point of being a cliche. My teacher's teacher for the one-on-one clinical breathwork facilitation modality I learned really deconstructed this whole idea in a post on social media which I really took to.
The truth is that what doesn't kill us does not always make us stronger. People can cause permanent damage to themselves by over-training on a number of stressors under the guise of wanting to become stronger. This can happen from an acute stimulus the body has no ability to adapt to (e.g. a weightlifter getting crushed under a semi truck). It can also happen through chronic stressors. The accumulations of strain on the body and emotions with no diligence paid toward discharging that allostatic load can make returning to homeostasis all the harder, if not impossible.
Some people simply receive too much damage (physical or emotional) for themselves to be put back together in such a way that they return to their original quality of life or ease. There can be a quality of hubris among those who value pushing themselves and pushing themselves, dismissing any form self-care as self-importance or weakness, like they can brute-force the locks set in place by the universe upon their state and station.
Another side to this, which is less obnoxious but no less problematic, are those work in a variety of the healing professions who think all suffering can be eliminated by everyone just going carnivore or using essential oils or never touching a grocer's receipt or doing breathwork or meditation. That thinking also pervades the allopathic and transhumanist medical system wanting to treat aging and death like they are curable diseases.
It doesn't mean we should wrap ourselves in down and never try and become stronger in all the ways that we can. The virtue is between the extremes, like Aristotle said once. Relaxation is fundamentally about surrendering to what is, and what and where we are in the now. All the emphasis on the personal power of the self, either as an achiever or a healer in a mass culture which lacks wisdom, is all about the force and the power, and never about the surrender.