Why does nuget keep the lastest xunit package?

Why does nuget keep the lastest xunit package?

Let's assume that there is one project depended on the xunit-v1.9.1
package and its output assembly is published as nuget pacakge. Now, if the
package is installed using the Install-Package command, the depended xunit
package will be installed as v1.9.2 not v1.9.1.
I cannot observe this case in other packages. Is there any point making
this case?
At this question, the nuget version is v2.7.



[update]
The following code snippet is part of the nuspec file of my test project
mentioned above.
<dependencies>
<dependency id="xunit" version="1.9.1" />
<dependency id="Moq" version="4.0.10827"/>
</dependencies>
When I install my test project, the Moq package was installed as the same
version specified above but the recent Moq version is v4.1.1308.2321,
which is not breaking change according to semver. On the contrary, the
xunit package was installed as the lastest v1.9.2.