Bewildered?
No....... I've understood for quite a long time now that there are a handful of suppliers for the various components in the cam industry.
A few spring coilers, a few lifter manufacturers, a few cam core sippliers...... The stuff between brands is more the same than it is different.

How sure are you that your springs are set up with the pressures/clearances you say they are?
The reason I ask is, when I've installed the beehive spring that's normally used in that application on the RPM heads, I've had to use a +.050 lock to get the installed height tall enough. From the pics of your heads, yours appear to have the std height locks.
I've also seen where the coil bind height on that spring can vary quite a bit.
If you happened to have the springs installed on the short side, and one or two go into coil bind at a height taller than spec, then you could have a situation where they are starting to stack up, which can really cause some issues with the lifters.

With those springs in particular, I make sure to check the coil bind height on evey one, and adjust the installed height where needed.

Also, the HS "1.5" rockers are usually closer to 1.55, so you could have more net lift at the valve than what's on paper.
This is tough with hyd lifters since they bleed down when you're doing this type of test/measurement, so it really needs to be done with a solid lifter, or in this case, a solid roller.

The biggest difference I saw on the lifters was yours have a completely shrouded wheel, whereas mine have the wheel exposed(although it's tough to make it out in my pic).