That is an ASSUMPTION you are making.
Reporters get background information from more that one source and Obama had been in HI for three years at that point. It was NOT a quote. The reporters story could have been edited and “2 years” could get typeset as “seven years” going from notes to print.
Yes, it is a discrepancy in the narrative, but you have reported no confirmation for your 1955 theory except for the vague decades-old Massena memories which don't claim 1955 either, IIRC.
YOU STILL PROTEST TOO MUCH. And if you go back to the Maseno school article I posted, you will find that the teacher was NOT relying on a decades old memory...he gave the details to the interviewer FROM THE RECORD!