so often -- every so often?

[Cookies0090]

Hi,

But the city has made clear that it favors more prestigious schools and more ambitious proposals. Officials would not release the actual proposals, but Cornell, which would run its school in partnership with Technion-Israel Institute of Technology, has plans for about two million square feet, roughly double the size of Columbia’s, which is in turn much larger than the others’. Julie Wood, deputy press secretary for the mayor, said in an e-mail that each remaining contender “has a game-changing project queued up.” ...

Cornell officials declined to respond directly to Stanford’s withdrawal. Instead, it dropped its own bombshell with the record gift, with Dr. Skorton saying in a statement that “our entire community has come together, in a way that happens only so often in an institution’s history, with winning ideas, energy and the creativity that the mayor’s challenge deserves.
(Stanford Ends Effort to Build New York Arm; the NY Times)

Does the sentence (the bold part) make sense to you? Is "so often" here a printing error for "every so often"?

[Gillnetter]

Hi,

But the city has made clear that it favors more prestigious schools and more ambitious proposals. Officials would not release the actual proposals, but Cornell, which would run its school in partnership with Technion-Israel Institute of Technology, has plans for about two million square feet, roughly double the size of Columbia’s, which is in turn much larger than the others’. Julie Wood, deputy press secretary for the mayor, said in an e-mail that each remaining contender “has a game-changing project queued up.” ...

Cornell officials declined to respond directly to Stanford’s withdrawal. Instead, it dropped its own bombshell with the record gift, with Dr. Skorton saying in a statement that “our entire community has come together, in a way that happens only so often in an institution’s history, with winning ideas, energy and the creativity that the mayor’s challenge deserves.
(Stanford Ends Effort to Build New York Arm; the NY Times)

Does the sentence (the bold part) make sense to you? Is "so often" here a printing error for "every so often"?

This event occurs infrequently to an institution - not very often and not on any schedule. If it was "ever so often (not every)" it would mean that this event occurs more than once and on some sort of schedule. For example, Halley's Comet is seen on earth ever so often - about every 75 years.