Not just gut flora. High levels of circulating xylitol (and erythritol for that matter) have been shown in both mouse models and humans to be associated with increased platelet reactivity and elevated 3-year risk of major cardiovascular events.

But we're talking significant levels of xylitol/erythritol, such as from keto-friendly ice cream and drinks, not the modest levels from chewing gum, and the dental benefits are well established.

It certainly is a problem for the guts of some people.

There is a hilarious Amazon review describing the effects of sugar-free gummy bears in rather graphic details.

https://old.reddit.com/r/funny/comments/1ktb95/most_helpful_...

I don't know if it is xylitol, but if not, it is another sugar alcohol, like sorbitol, maltitol, erythritol,... that have similar properties

Excessive xylitol consumption causes digestive problems, yes.