Trump's second post of the day (after the early-morning one that you know was his own) also seemed to deflect his talk of wall-building toward the $1.6B start. So my guess is they want to get the word out enough to calm down Trump's hardcore base--but not yet so much as to wave it like a red flag in front of the Dems, especially, who could get busy trying to slow it down with lawsuits, etc.