I don't think this was the issue...changing the cap for a new one was always part of the instructions for changing the battery/removing the cover. I purchased an official Suunto battery kit with new cover about 3 months before the recall just to have as a backup. My transmitter battery was going strong so I had not use the kit yet when the opportunity came to send the transmitter in for the recall inspection. The transmitter cover in my battery kit does not have the white "O" printed on it. I called Suunto about using the non-"O" cover in the future and they said there were no issues with the cover specifically. They did not get into specifics but eluded to a the fast increase in pressure within the transmitter when opening the cylinder valve. I believe when they realized they should have had pressure reducers installed from the start they decided to recall, inspetc, and provide the pressure reducers upon return...for the hassle they also changed the battery, cover, and o-ring at no cost to the owner. I believe it was a recognition that their product had the potential to be dangerous and that by recalling, inspecting, and returning with the additional pieces they substantially lowered the chances of an issue from occurring and substantially reduced their potential liability.
That is just my thoughts/belief...I have no concrete data to back my notion up.
-Z