I wouldn't worry too much. It's not atypical of Ginn or of pre-season action. Ginn was dubbed by one of the Dolphins beat writers last week as The Invisible Man, then he had a strong showing in their preseason game - a couple catches, an end around and he drew a interference penalty as the Dolphins went to him repeatedly on two drives.
In this game, they didn't. I wouldn't put too much stock into it. They're trying to determine their pecking order after Ginn and Bess. Camarillo looks like he won't be back quite as soon or as effective as initially thought following strong OTAs. Patrick Turner has been intriguing with his size and abilities in the red zone. Brian Hartline, well, I don't know what to make of him. I tend to be Big 10 partial (roll eyes) but he never impressed me much at tOSU and I suspect his value is mostly special teams/returns. I think Sporano, Tuna and Ireland are trying to see what they have in London, Armstrong, Hartline and Turner. It's been a close, heated battle there. I wouldn't be shocked if Camarillo goes on the PUP or gets cut, depending on how Armstrong and London do in the next week or two.
As far as Ginn goes, he is inconsistent. So, it could be by design or due to good defensive coverage and pressure applied to him. He has to prove he can handle physical corners at the line and effectively and consistently get separation (and quickly). He'll be fine.