If you are using the heading for an anchor I suggest assigning a custom ID. Most headings are not an anchor and so would not have any effect on the user or the site they are just a unique reference for SEO purposes. At this time I don’t have plans to auto assign a pretty ID. It’s more complex then what I believe you are thinking.
And again it’s important to note the TOC block only assigns on load if the ID is not already assigned. In most situations, the ID should be assigned and confirmed unique by you if you want it to be an anchor.