Initially while provisioning a system, it has an environment set based on the host group.

If we change the puppet environment, we get the following warning:

Local environment: "xxxxxxx" doesn't match server specified node environment "yyyyyyyyy", switching agent to "yyyyyyyyy".

It's expected that it's because there is a mismatch between what was originally set in /etc/puppet/puppet.conf on the client and what is currently in Foreman under the host details.
Puppet honors the new environment and applies changes accordingly, but users want the puppet.conf to reflect changes made in Foreman so there is no confusion about what environment is to be used.
If the settings are inconsistent, you don't know if you can trust the settings depending which way you check the information. It also causes confusion when validating configurations.
Suggested resolution is to use Puppet to manage puppet.conf.

Steps to reproduce:
1) provision a host with Puppet environment
2) change Puppet environment for the host in Foreman, run Puppet