Permissions-Policy whic are added ASP.NET web.config files are not worked

Question

I added below permission policy header to ASP.NET web.config file in my project

<httpProtocol>
  <customHeaders>
    <add name="Permissions-Policy" value="fullscreen=();"/>
  </customHeaders>
</httpProtocol>

According to the policy fullscreen function should not be worked, but it is working. What i have missed here ?

Could some one please advice me to over come this issue