Yes, it is true that putting speakers so close to the back wall would affect sound. Google "speaker boundary interference response" (SBIR) for more reading on this, but the general idea is if a speaker is too close to a wall, it will use the wall to "plane" or "bloom" the wave forms generated from the speaker drivers.
Also, like Erik said, do not get a speaker with a rear port if you are going to push it up against the wall. Make sure it has a front port.
Also, like Erik said, do not get a speaker with a rear port if you are going to push it up against the wall. Make sure it has a front port.