GetQueryStringParameters normalises to Lowercase.

[S-Tasker]

QueryString parameters should not be normalised to lower case unless specifically requested, as per RFC-3986 (section 6.2.2.1).

Excerpt:

For all URIs, the hexadecimal digits within a percent-encoding
triplet (e.g., "%3a" versus "%3A") are case-insensitive and therefore
should be normalized to use uppercase letters for the digits A-F.

When a URI uses components of the generic syntax, the component
syntax equivalence rules always apply; namely, that the scheme and
host are case-insensitive and therefore should be normalized to
lowercase. For example, the URI HTTP://www.EXAMPLE.com/ is
equivalent to http://www.example.com/. The other generic syntax
components are assumed to be case-sensitive unless specifically
defined otherwise by the scheme (see Section 6.2.3).

The issue is in UriTemplateExtensions.cs, line 80.