Aguero will not face retrospective action over his two-footed challenge on the Chelsea defender in Sunday's FA Cup semi-final victory at Wembley.
With referee Chris Foy having awarded a free-kick at the time of the incident, the Football Association considers the matter to have been dealt with.
Some pundits have said the tackle warranted a red card but the FA does not like to 're-referee' incidents which have been seen by officials.
Platt said: "I wasn't surprised, based on the rules the FA has put in place if the officials have seen it.
"There have been precedents set, and not only have precedents been set, they've actually gone on record and said if that's the case - I wasn't surprised.
"The rules are the rules. We don't make them up, we adhere by them."