Interesting point of discussion, but I would still say 'no'. For almost the entirety of the BB era the Pats have made a point to try to get two tight ends that are receiving threats going all the way back to Fauria/Graham, Graham/Watson, Gronk/Hernandez, and Gronk/Bennett. Sure, they might have a third tight end be a blocking specialist like Alge Crumpler or Jed Weaver (I think that was his name), but historically they've liked two tight ends to be receiving threats.
Given that history and the fact that Allen showed some promise as a receiving threat in Indy, I'm guessing he was brought in to continue to show signs of life in the receiving game (signs that weren't shown until yesterday). Plus, the fact that Bennett comes in and gets more receptions in one game than Allen has had for all year is just further indication that they want that additional threat.
You're correct that BB has tried to get 2 TE receiving threats. But it hasn't worked as well as you said. Most people would question you saying Graham/Watson as dual threats since Graham became one of the best blocking TEs the game has seen while here and didn't do a lot in the receiving game.
Most people have said it was only when BB got the Gronk/Hernandez duo that he truly got the 2 receiving TE threats he wanted. He got the Hybrid in Gronk and the almost pure receiver in Hernandez. With Bennett, it was duplicated, though they only played in 3 (?) games together..
2000 - Bjornson, Wiggins, Rutledge
2001 - Wiggins, Rutledge
2002- Fauria, Cleeland, Graham
2003 - Fauria, Graham
2004 - Fauria, Graham (Watson was IRed after 1 game)
2005 - Watson, Graham, Fauria
2006 - Watson, Graham, Thomas
2007 - Watson, Thomas (2 games), K. Brady
2008 - Watson, Thomas
2009 - Watson, Baker
2010 - Gronkowski, Hernandez, Crumpler
2011 - Gronkowski, Hernandez
2012 - Gronkowski, Hernandez, Fells, Hoomanawanui
2013 - Gronkowski, Hoomanawanui, Mulligan
2014 - Gronkowski, Tim Wright, Hoomanawanui
2015 - Gronkowski, Scott Chandler, Michael Williams, Asante Cleveland
2016 - Gronkowski, Bennett, Lengel
2017 - Gronkowski, Allen, Hollister, Bennett.