Could be. Remember that Light Plate is the first armor you get access to, and is heavy for the protection it provides. The comparison to make is with Chainmail, which would be lighter (less initiative penalty) and way less defence. Masterwork Chain is the light version of Full Plate (the ultimate non-magic armor type) and will have way less defence than full plate.

I see no problem here.

It's not confusing at all, maybe you haven't looked at the tech trees properly.

Understand;

If you have masterwork chain trait then... chainmail upgrades to masterwork chain as you get higher on the military tech tree

If you have light plate trait then...  light plate upgrades to heavy plate

If you have both... light plate upgrades to masterwork chain

If you have none... chainmail upgrades to heavy plate

Something that might help in the clarification would be to have text below each one since there's a space for it:

• Masterwork Chain Armor

Replaces Plate Mail and requires the Chain Mail trait

• Light Plate Mail Armor

Replaces Chain Mail and requires the Plate Mail trait

Did I get those descriptions right?

Maybe the items could have the same description (or some variant of my description above)?

the tooltips for those traits should be adjusted anyway - it says that light plate is "heavier" - which is probably a relic from the encumbrance system (i think a suit of chain had a weight of 15 and a suit of light plate was 30 or something). the text should be updated to indicate that the light plate has a higher penalty to initiative. i guess while they're at it, they could just copy & paste the text to the armor item.