Reproduced 3/3 times. Issue does not occur in //UE5/Release-5.0 - CL 20979098 Binary. Confirmed Regression.
Actual Result: Both UPROPERTIES are displayed in Blueprint Editor, and the EditInstanceOnly UPROPERTY can be modified, which affects all existing Instances
Expected Result: These UPROPERTIES should only be accessible/visible in Instances
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-171504 in the post.