"More important is the fact that Sam Houston had, days earlier, ordered the mission evacuated, the men there to join his own army further north; by defying his order the men of the Alamo were staging a sort of mutiny."
I was taught in High School Texas History that Col. Travis made the stand at the Alamo to buy Sam Houston's Army more time to assemble volunteers to face Santa Ana.
I'm left wondering about your motives in cheapening a great act of heroism by referring to it as "a sort of mutiny."
The usual story is that the stand at the Alamo was to "buy time" for Houston, but the Alamo was hardly an obstruction to Santa Ana's army. The Mexican Army could easily have skirted around it, leaving the Texans inside looking like deserters from Houston's forces. Exactly why Santa Ana made a point of stopping in San Antonio and laying siege to the mission is conjectural; he may have wanted a quick victory to encourage his troops, he may have wanted to make an example to intimidate other Texans, etc.
Yes, the Texans at the Alamo had received a direct order from Houston clearly instructing them to abandon the mission and join the main Texas forces, and they deliberately disobeyed it.