Why boarding a drone ship could escalate quickly

Would nations take an attack on drone ships seriously, or does the lack of a crew make the difference?

They are likely to take it seriously, especially a boarding attempt, because it risks capture of valuable technology and data as well as setting a precedent.

Destroying an aerial drone differs from boarding a drone ship. A downed aircraft may be badly damaged, and salt water can make useful recovery still harder. An intact uncrewed ship can expose valuable technology, data, and communications systems to whoever boards it. Seizure also establishes a precedent that states have strong reasons to resist before it becomes routine. The response depends on the platform, the information at risk, and the manner of the attack as well as whether a crew is aboard.