Because Amy felt embarrassed and wanted to create an illusion that her relationship with Benjamin was still decent.
As a result, this illusion actually deceived Adam.
It made Adam mistakenly believe that his sister and Benjamin had a good relationship. Otherwise, how could she be living in Benjamin's mansion?
It should be noted that in that household, apart from Martina, his sister was the second woman who could reside there. Wasn't that special enough?
Unfortunately, reality slapped Adam hard in the face.
Even though Adam felt a hint of humiliation deep inside, he still followed Benjamin's intention and replied, "I won't make thoughtless remarks anymore. If you have no interest in my sister, then she will remain just my sister."
Fortunately, Adam's mind was still clear. If he had remained stubborn and unrepentant, the consequences could have been even more severe.