Following up, the period immediately proceeding the “restoration” of emperor, and the early years of the administration were quite turbulent, including a rebellion or two. The collection of groups who were involved in overthrowing the bakufu (government led by the shogun) obviously had varying aims and interests, which evolved over this period.
Because no single han was strong enough to take on the bakufu themselves, it took a collection of the strongest ones to make it possible. Rallying around the banner of emperor (who traditionally did not have actual political power) was a politically calculated step to gain more people onto their side.
They pro “imperial” forces never intended to actually turn real political power over to the emperor, but to form an oligarchy as the administration in the emperor’s government.
The rallying cry of this collection was Sonnō jōi (尊皇攘夷, Revere the Emperor, Expel the Barbarians), which was useful in order to gather more people into the anti-bakufu camp.
In 1868, the transition to an imperial system was just starting, the Boshin War was still currently being fought, and the end of the Tokugawa family was still not certain.
As part of the strategy of the Satsuma - Choshu alliance, they removed land had directly been under the control of the Tokugawa family and bakufu administration, and rather than dividing it up among themselves, which would have cost them support by the other daimyo, they placed it under the emperor, while maintaining control of it as the oligarchy who ran the administration. Slick.
As the idea in the final years of the 1860s and the early 1870s, was to create a centralization of power based on imperial system, it makes sense for them to look to China as a model of imperial (emperor-run) power. If this WAG is correct, then it would be understandable that this is the reason they borrowed the term 県 for the land confiscated from the Tokugawa family.
My (brief) study of this subject supports cckerberos theory, but it would be interesting if others have more insight.