It really immaterial what the estimates of gifts were. In 2012, the FAA was ordered to have regulations in place by september 2015, to handle commercial UAS. They were explicitly prohibited from regulating hobby drones. UAS tech was blossoming, and the FAA knew this long ago.
In Sept 2015, they updated their AC-91 57, which had to do with hobby UAS. They had been running some tests for commercial flights, handing out occasional section 333 exceptions to movie industries and others.
In Nov 2015, they got feedback that this year's sales were expected to be around 1M+. Fearing what you stated, dumb people flying drones into manned aircraft, they cobbled together a site incredibly quickly requiring registration of all aircraft. They loosely, and wrongly, interpreted the law stating that they may not promulgate restrictions or regulations that affect any hobby or recreational UAS, to read that they may not promulgate rules that affect only hobby or recreational UAS. Despite having 3 years to see this and come up with regulations, they bypassed the mandatory 60 days of public comment stating that it was an emergency situation (caused by their own inaction, which case law has shown cannot be used as an excuse to consider it an emergency).
They are now requiring everyone 13 years old and up to publicly register their names and addresses. In a searchable database, publicly accessible. Failure to do this carries up to a 3 year jail sentence and $25,000 fine. This is the potential penalty for little johnny flying a drone at TWO INCHES above ground level in his own back yard. No joke, the FAA has asserted control from the top of a blade of grass (their words) to the top of the atmosphere. If a neighbor complains about little johnny in his back yard playing with a helicopter that looks like it weights more than 500g, a federal cop has probable cause.
The FAA had orders to have this in place 3 years ago, and failed. Based on that failure, they're claiming an emergency gives them rights to break the law and forgo public comment. The estimates for drone gifts don't matter... the FAA was given 3 years to solve this before it became an issue. Now they are breaking the law that literally requires an act of congress to reverse. (See section 336 which prohibits them from regulating hobby craft.)
There were so many other ways they could have handled this correctly. They could have requested hobby drone manufacturers enclose a copy of AC-91 57 in their packaging. They could have petitioned congress to change the law, allowing some regulation of hobby drones. They could have made a system that didn't allow searching for names and addresses of minors. They could have asked drone manufacturers to, by default, activate geofencing (but not require it). I'm sure there are other even better ways to handle this, too.