If you create a new VM or edit an existing VM to add both a 'preferredDuringSchedulingIgnoredDuringExecution' and 'requiredDuringSchedulingIgnoredDuringExecution' rule for nodeAffinity, the requiredDuringSchedulingIgnoredDuringExecution is always removed or overwritten.

4.17.5

Always

1. New VM from Template - using a default rhel 9 is fine
2. Click the Scheduling tab 
3. Click Affinity rules
4. Add affinity rule
Type: Node Affinity
Condition: Required during scheduling
5. Add expression
kubernetes.io/os In linux
6. Save affinity rule
7. Add affinity rule
Type: Node Affinity
Condition: Perferred during scheduling
Weight: 50 (doesn't really matter for this)
8. Add expression - Nodes have a label performance with a value of standard and high
performance In standard
9. Save affinity rule

Now it shows both rules and 17 Nodes matching, 3 matching preferred Nodes found

Click Apply Rules

Now under: Affinity rules

It only shows: 1 affinity rules

    spec:
      affinity:
        nodeAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
            - preference:
                matchExpressions:
                  - key: performnce
                    operator: In
                    values:
                      - standard
              weight: 50

    spec:
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
              - matchExpressions:
                  - key: kubernetes.io/os
                    operator: In
                    values:
                      - linux

    spec:
      affinity:
        nodeAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
            - preference:
                matchExpressions:
                  - key: performnce
                    operator: In
                    values:
                      - standard
              weight: 50

Only preferredDuringSchedulingIgnoredDuringExecution gets applies. 

preferredDuringSchedulingIgnoredDuringExecution and requiredDuringSchedulingIgnoredDuringExecution should be applied