This isn't anything new. Behavior present since v0.55.0.

content/
├── p1.md  <-- tags: ["a b"]
└── p2.md  <-- tags: ["a-b"]

public/
├── p1/
│   └── index.html
├── p2/
│   └── index.html
├── tags/
│   ├── a-b/
│   │   └── index.html   <-- page collision
│   └── index.html
└── index.html

Expected hugo --printPathWarnings to detect collision.

By comparison, content tagged with "a,b" and "a;b" report a page collision (as expected), because they are both published to public/tags/ab/index.html.

See also:

• https://discourse.gohugo.io/t/limit-use-of-punctuation-within-taxonomy-terms/48638
• Add taxonomy term naming rules/guidelines hugoDocs#2465