Actually, we have no way of knowing (nor do the DHS attendees) exactly what was being used for the 'demos' - are the trainers mixing chemicals in front of the class and then using those very same containers to detonate in the controlled tests?

Sorry to play the skeptic here, but even if it looks like that's what they're doing, in reality what you have is:

1) the actual explosions are caused by pre-hidden solid explosive charges, or

2) the liquid explosives were created in controlled lab conditions which are virtually impossible to replicate on board an aircraft

I wouldn't put it past DHS management to pull the wool over the eyes of their own employees.