Oh there's already a report about it. But yes it looks like the same problem.
I would consider it a bug, because the only way to have the full blueprint be built is with some kind of workaround (like building foundation north and south before pasting the blueprint, or pasting the blueprint and ...

This was also happening in 2.0.15.
When building a space platform via blueprint but the platform is veeeery long, it will get trimmed.

Reproducing:
Use my blueprint on a new space platform.
You'll notice how you can't see the south part of it, and the requested materials are less than the ones in ...

I loaded up a savegame and tried this again.
You are indeed correct, but the items were indeed missing in my case.

When I place it with Q, the equipment grid gets cleared, with all items marked with an X so bots take the items out.
Turns out the items were not in the logistic network, because they ...

I sent my spidertron, with some stuff in its equipment grid, to another planet. The equipment grid still shows when it is in the cargo landing pad, so I pick it up with Q and place a ghost.
When I did this, the spidertron was successfully placed (it's the only one in the logistics system in there ...

I have also seen some oddities with the EM plant when crafting electrolyte. If I place it, plumb the inputs, and let it run without anything connected to the outputs, the electrolyte just vanishes, rather than building up in the output slot. After something is connected, once that is full, then ...