Layer dimming not working. What am I doing wrong?

[#1]

Fifteen years ago, the first thing I learned when I first opened Illustrator was to layer lock and turn it into a template. What changed?

I have two layers with different objects in each. I double click my bottom layer and choose: Template + Dim images to 50%.

Layer locks, but opacity stays the same. I'm on the latest AI. What's going on?

[#2]

Fifteen years ago, the first thing I learned when I first opened Illustrator was to layer lock and turn it into a template. What changed?

I have two layers with different objects in each. I double click my bottom layer and choose: Template + Dim images to 50%.

Layer locks, but opacity stays the same. I'm on the latest AI. What's going on?

[#3]

Are the objects on the layer images? Because that's what that option dims, not regular drawing objects.

[#4]

It's a JPG.

[#5]

Please show a screenshot of the problem. Layers panel should be in it.