According to the article, upon returning from their fact-finding mission, they had a closed-door meeting where they said one of the FACTS they had FOUND was that people couldn’t get the information they needed during the initial stages of the crisis.
There is nothing in the article you posted which suggests the IAEA’s fact-finding mission was hampered by a lack of information. It might have been, but that wasn’t in the article you posted.
The IAEA presented the whitewash some of us knew to expect in their official report - praising the Japanese response. Then they went home and ‘leaked’ that they didn’t get the information re radiation released they wanted.