After renewing the SSL certificate, signing certificate still shows as an expired certificate in the device.

Expired signing certificates are actually a digital signature cert for profiles. A digital signature of a profile is included in the profile data. The digital signature block contains information about the cert that was used to sign digitally, which is what iOS shows. A digital signature is established when the profile is downloaded from the server with the digital signing cert server is/was using at that time. Digital signature never changes. Changing the SSL cert on the server, even if it does change the digital signing cert if the server uses the same for both purposes, will have no impact on existing state on the device.

Problem Cause

This is as per the design. Expired signing certificate are actually a digital signature cert for profiles. Digital signature of a profile is included in the profile data. Digital signature block contains information about the cert that was used to sign digitally, which is what iOS shows.