First it is just the IP and phone number. Then, it will be extended to contacts. Because, why not, that can be useful also for "terrorist investigations". Then it will be chat history,because it makes sense, the police has a warrant... And telegram is technically able to...
Also, clever poll tactic to put the option 1 as looking 'moderate' in front of other extreme options.
Also, for the fighting "terrorism" argument, just remember that we are all terrorists for Russia, and that even in Europe (Germany, France, ...), A lot of high ranking gov and police officials were found guilty of corruption or abusing the system for their own interests!