It was a mistake for some economists to expect the Federal Reserve to express concern about rising inflation in its policy statement Wednesday, says CNBC contributor Ron Insana.

The Fed's predictions for both inflation and interest rates remain below those of financial market participants, he writes in a commentary for CNBC.

Most Fed policymakers forecast that the personal consumption expenditures (PCE) price index will rise 1.5 percent to 1.6 percent this year. The Fed has a 2 percent target for that inflation rate. The PCE price index gained 1.6 percent in the year through April.

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"The Yellen Fed is preoccupied with long-term unemployment and excess slack in the labor market, not phantom inflation that has bounced recently based on either temporary factors or calculation quirks in compiling the consumer price index [CPI]," Insana argues.

The CPI climbed 2.1 percent in the year through May.

Until the economy starts "firing on all cylinders, I would not expect that big surprise from the Fed that everyone is waiting for — a pre-emptive strike on inflation through a premature hike in interest rates," he states.

"The Fed knows what that will do to the economy's growth prospects and it certainly is not willing to risk trading full employment for below trend inflation."

Some investors see the Fed's unchanged policy stance as positive for stocks.

"There was some expectation that this could be a little more hawkish given that some inflation measures had come up," Michael Arone, chief investment strategist at State Street Global Advisors, tells Bloomberg.

"Now that the Fed has not interpreted that in a way that means the economy is overheating, I think the market will be pleased with that result."

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