Definitely report them to Airbnb. This is a reasonable security concern. If you click on their profile, just under the users name and location will be a small grey flag and "report this user". Click on it and highlight your concerns.
We had a similar issue where a guest requested to book for 6 adults...and then as the discussion went on, admitted the traveling party was 6 adults and 2 children. Our property is for a MAX 4 people. After declining their reservation, I received a new enquiry a few weeks later for 4 people, from someone I thought was a different guest. The profile name and photo had been changed (verified ID, which we require, stayed on the profile, despite the name and profile change).
It was only a week before their confirmed booking that I noticed that my email account had 'bundled' the emails from these supposed two separate guests together - ie. they were from the exact same anonymous Airbnb guest account. When confronted the guest refused to cancel their reservation, arrogantly telling me that they would force me to cancel and be penalised as a host for canceling. I called Airbnb and after a bit of convincing and referring them to the communication with the guest (thankfully all in writing within Airbnb), Airbnb cancelled the guests booking without penalty to me. They wouldn't tell me what they did at the other end, but the guests' profile was disappointingly not deleted/ removed.
These security issues could definitely be more serious than in our situation, and the simple fact is that it is a fraudulent representation, and contrary to Airbnb's ethos of community and openness.