Should UrlHelper::parse() unify the leading slash for local URLs?

Problem/Motivation

I just ran into a case in a redirect contrib module: #3448469: "Delete redirects defined in the spreadsheet" misses to remove leading slash normalization where UrlHelper::parse() is used.

Drupal 8+ expects leading slashes for internal paths, but currently that's not represented or unified in that helper method.

So currently the output for
/node/123
is
/node/123

and for
node/123
is
node/123

and I think it makes sense to discuss if this internal Drupal helper method shouldn't better returned the unified Drupal path /node/123 always with the leading slash, despite the input!

In this example it leads to two different check sums for the same path in Drupal.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet