Actually, not true. Right now, Ebron (1.6), Doyle (1.65), Pascal (1.5), and Rogers (2.09) all have better separation stats than TY (1.04). This doesn't mean TY stinks or is slow, it means he's getting doubled and is the focus of the opponents D.
Announcers also commented several times about open WRs downfield that weren't seen (Cain was one specifically mentioned). JB also ranks 28th in AGG% (% of time a QB tries to force it into tight window), which is likely a result of him keying in on a well covered TY too much.