The Sermon on the Mount (Matt 5 ff) was not all parables. Thus it is false to assume all of the language God used in transmitting the creation story was cryptic rather than clearly stated.
You are right, by accident. The sermon on the mount was not a parable.
The first point is you missed the point of the discussion with the other person, that is, “parable” is inadequate as a rendering, to describe how God speaks. When translating the Bible into English there are not exact equivalent words, there are only approximations; in addition to that the translators have preconceived ideas.
The Hebrew word rendered “parable” means (according to Strong) sense of superior mental action; a pithy maxim, usually of a metaphorical nature, hence a simile. Byword, like, parable, proverb.
The Greek word rendered “parable” only means a fraction of the Hebrew; a similitude, a fictitious narrative; comparison, figure, parable, proverb.
Now because the apostle reported Jesus as saying He was fulfilling OT prophesy when He spoke, the OT definition applies (assuming Strong got it right). Also Jesus spoke in that manner except when taking privately with the apostles.
At the sermon on the mount, even though Jesus is sitting with a multitude, it is His apostles He is teaching, therefore not the way He would stand and address the multitude. Any apostle may assume Jesus is talking to them, but not any multitude.
The crowd that overheard Him, speaking from a sitting position, were astonished. Ps 78:1-2, Give ear, O my people, to my Law: incline your ears to the words of my mouth. 2. I will open my mouth (in the manner in which I talk); I will utter dark sayings of old.
