Just back from watching it.
This message isn't for the Autists alone.
I don't say that you are not right. I'm thinking about the meaning of 'reflection' according to Merriam-Webster.
Trump wishes a great President's Day.
And then he says "but".
And then he urges or admonishes, to be very(!) thoughtful or very(!) deliberate.
This sounds also like a warning or threat.
To know what this means, we would have to know, who his special audience is for the "but"-part.
First part of his tweet is for general public, I guess.
Second part is to a special audience: Be very thoughtful, be very deliberate, be very reflective.
Whom is he addressing in the second part of his tweet?
Ty. Maybe he's telling certain persons or groups to use this day to be very(!) reflective on what they did wrong.
Trump tweeted "Whitewater" yesterday. (CF)
I think, he says that the bad actors should use this day to be "very reflective" on their past wrongdoings. Like punishment/ justice will come.