The answer received in my email for the above question is incorrect.
As per the answer I received it was mention that everything under root(/) folder will be deleted.
I provided answer is correct only if statfilelevel=0.
But in most practical cases no one uses statfilelevel=0
The invalidation of the page for this question depends on the statfilelevel setting in dispatcher.any file
Please see the document provided by Adobe here
Invalidating Files by Folder Level
Use the /statfileslevel property to selectively invalidate cached files according to their path:

Dispatcher creates .stat files in each folder from the docroot folder down to the level that you specify. The docroot folder is level 0.
When a file is updated, Dispatcher locates the folder on the file path that is at the statfileslevel, and invalidates all files below that folder.

in context of below question
What does the glob /invalidate {/0001 {/glob “*.html” /type “allow” }} in dispatcher.any file enforce the dispatcher to do when the Web page /content/mypage.html gets activated?

answer : in actual it invalidates not delete , can you please look?

Automatic invalidation is typically used for HTML pages. HTML pages often contain links to other pages, making it difficult to determine whether a content update affects a page. To make sure that all relevent pages are invalidated when content is updated, automatically invalidate all HTML pages. The following configuration invalidates all HTML pages:

/invalidate
{
/0000 { /glob “*” /type “deny” }
/0001 { /glob “*.html” /type “allow” }
}