Correct, and DA Carson the renowned Greek scholar explains exactly why your inferential conclusion is wrong.
Your appeal to DA Carson as a "renowned Greek scholar" is fallacious and misleading. DA Carson was NOT analysing the Greek but was making a common error of converting Greek to Aramaic then trying to formulate and argument from the Aramaic. There is NO proof that Jesus was speaking in Aramaic only speculation but actually makes no differenc. The FACT of the matter is that the Holy Spirit inspired the New Testament to be written in Greek, a language that makes a distinct difference between Petra and Petros.
Translating the Greek which was inspired by the Holy Spirit into Aramaic or Hebrew to try to formulate an argument is second guessing the Holy Spirit and changing what He inspired to be written. Not a wise move.
There is also another problem with the DA Carson attempt to work Aramaic into the argument. Even if Jesus was speaking Aramaic it proves nothing. While Kepha can be translated Petros in Greek it is not proven that Jesus used Kepha for petra as there are other words in both Hebrew and Aramaic for petra. Even DA Carson admits such as seen here
Your appeal to Carson is worthless.