I recommended this blog and take your point that the cop's report was apparently tweaked to make them look better. Even if my following speculative scenario is completely correct, it does not change the significance of your point.

First, I am assuming that the neighborhood was a predominately white one. That would mean that the cop would probably, even if not consciously, expect that the house he was approaching was the home of a white person. The fact that a single officer responded to the call and upon arriving at the scene saw a nice car or limousine [I'm guessing here again] parked in the driveway and then walked up to the door and rang the bell would indicate to me that , despite his training and his long history of police experience, or maybe because of it, he was not expecting a criminal to answer the door. If he was consciously or unconsciously expecting a white person to answer the door and a black person did instead, he might have reacted with some surprise and shown by as little as a subtle change in body language that he wondered why he was looking at a black man. This could [possibly] be what first offended Gates.
If the dispatcher had, in fact, stated that a black person was seen entering the house Crowley may have reacted differently when Gates answered the door. Who knows?

The dispatcher's call to Crowley states "unknown on race, one may be Hispanic. I'm not sure." Dispatcher also says, "They have suitcases."

The police report states the Crowley talked to Lucia Whalen on the sidewalk in front of the house. "told me that it was she who called. She went on to tell me that she observed what appeared to be two black men with backpacks on the porch of -- Ware street. She told me her suspicions were aroused when she observed one of the men wedging his shoulder into the door as if he were trying to force entry."

Wendy Murphy, attorney for Lucia Whalen, has a different version

But Murphy, speaking on Whalen's behalf, says the only interaction between Whalen and Crowley occurred at the scene when she gestured to him and told him she was the 911 caller and he told her to stay where she was.

Another officer asked for her identification, but no officer interviewed her at the scene, Murphy says. Whalen stayed about five minutes and then left, Murphy says.

Murphy says Whalen does not want to reopen a debate or stir up controversy with the Cambridge police or with Gates. She says Whalen only wants to set the record straight

If we are to believe Whalen no discussion occurred at the scene. No talk of black men, backpacks, no discussion of observation of one wedging his shoulder into the door. If so it would appear that Crowley made up a whole conversation. I could understand a discrepancy between two versions and chalk it up to completely understandable bad memory. But I don't see how bad memory can create a conversation, albeit short, that didn't occur. Either Crowley or Whalen is lying. Considering that Whalen's version matches the 911 audio and the dispatchers call I tend to believe that is the correct version.

Bad memory can "create facts", and it is well documented. But it can impeach a witness.

The arrest was based on rather subtle distinctions. Was Prof. Gates yelling (report version) or wheezing (as he claims)? Were the onlookers startled by Gates, by the police, or not at all? How universal was the startlement (100 years ago, perhaps the report would mention seven onlookers, including two ladies of quality and sensitive disposition, three maids on the verge of panic and two gentlemen who were quite jolly about the incident).

By the way, Gates's residence is across the street from Harvard, and a Harvard maintenance person came to the scene, and was left taking care of the house. It seems that at that point there was no shred of suspicion of a crime in progress.

One can imagine a gentleman burglar arriving in a three piece suit, with a suitcase and in a taxi (if I were a burglar, this is what I would do). So definitely, some check was in order, but that being completed, hm.