As you pointed out, officially if you book through "opaque" channels you are not eligible for status recognition. There have been reports that some hilton properties recognize your status even with "opaque" bookings, although that does not guarantee they will continue to do so or do it upon your checkin.

"opaque" channels
Stays booked via "opaque" channels where the brand is unknown at the time of purchase are not Eligible Stays for the purpose of earning points, miles or stay credit toward Elite tier status, or the receipt of Elite tier benefits such as upgraded accommodations / amenities or access to health clubs.