He did, but he gave the excuse that it should be done by constitutional amendment. I think that shows he's quite ignorant on the subject, since it has never been done that way. If the people of DC voted for it, and adopted a proposed state constitution, I think it would be hard for him to say no. The only cases where some other people get to vote on a proposed statehood, has been where the new state is cut from a larger old state. In that case, the people of the whole old state have to approve it, before the division can take place.
People in other states have NEVER had a direct vote, and right in the constitution it says a simple majority. Not an elaborate constitutional amendment process.
We're flying electric helicopters on Mars yet you can't turn on your clothes dryer in Texas. That's because scientists are in charge of Mars, and Republicans are in charge of Texas.