I don’t want to get into what Ben Bradlee, the Watergate-era editor of the Washington Post, used to call a “defensive crouch,” but I’ve got a bone to pick with some of the headlines that came out of comScore’s July 2010 mobile market share report, issued Wednesday afternoon. For example:

• “Apple Continued To Lose U.S. Marketshare Despite Spike From iPhone 4 Sales” (mocoNews)

• “iPhone Marketshare Not Helped By iPhone 4” (Thoughts from the Sidelines)

First, let’s look at the numbers in pie chart form:

Note that I’ve drawn the second pie slightly larger than the first. That’s because the U.S. smartphone market grew 11% in the period covered by the data. So although comScore has Apple’s (AAPL) market share dropping 1.3 points from pie 1 to pie 2, its sales were actually increasing. Of the smartphone operating systems covered in the data, only Microsoft’s (MSFT) shrank.

But the bigger problem is hinted at in the title of the second chart: “3 Month Avg. Ending July 2010.” Can you guess what it is?

Consider the dates. The iPhone 4 was launched in the U.S. June 24 and promptly sold out. Sales been limited by short supplies ever since.

But more important, for most of the three months covered by the data in the second chart, the iPhone 4 wasn’t available for sale at all. And in fact, sales of the iPhone 4’s predecessors were almost certainly suppressed for all of May and most of June thanks to Gizmodo, which published photos of the new iPhone in mid-April. Who wants to buy the old phone when you know a new one (and price cuts on the old) are just around the corner?

This is not to take anything away from Google’s (GOOG) accomplishment. Android phones are selling like gangbusters and most experts agree that their market share will eventually overtake Apple’s.

But you can’t use comScore’s data as evidence that the iPhone 4 has somehow let its maker down.

[Follow Philip Elmer-DeWitt on Twitter @philiped]