Scalar param values array is empty in dynamic mat inst

In my BP’s construction graph I’m creating two new dynamic material instances. Each has a different parent but those parents have the same scalar parameters. I want to copy the settings from one MID to the other but for some reason the Scalar Parameter Values array of the MIDS are empty so nothing gets copied. If I print out the same array for the parent material instance then I get a correct number. What is going on?

Still appears like this in 4.15.1 - I made a bug for it, though if I had to put money on it, I’d guess it’s on purpose.