It is a bug that the ship is still commercial. I updated the code so that the 'commercial' designation requires at least 1 HS of engineering.
For v1.14, I've changed the error message to "Commercial designs require at least one Engineering Space". This will appear if the ship design is military, but the other reason for that is the lack of the 1HS engineering requirement.
Any chance we could get reduced requirements for very small ships?
I like to make small commercial sensor posts.
By small, I mean tiny.
For example, an 8-ton armorless station (just a 5-ton sensor and a 3-month deployment time; basically a glorified sensor buoy).
It seems incongruent to require 50 tons of engineering space for ships like this to qualify as commercial.