Im not sure about this, but i have a theory.I have a question. If you are non Uchiha and someone transplants an MS in you, can you still activate the normal Sharingan?
The reason kakashi cannot de activate the sharigan is because not only is he not an uchiha, it was already activated.
If it was de activated when obito gave it to him, it would serve as a normal eye because he cannot activate the sharigan.
Going by that if an ms user activated the ms and gave it to kakashi, he would be stuck with the ms and wouldnt be able to de activate it