They dont use tools. For inspection of random phones from non-suspects they just poke around by hand. Only when they find something do they employ actual tools.
Do you have a source on this? Preferably one that will be updated if the policy and practices change?
The only safe assumption is the worst case.
Why would they do this rather than simply image the device? How do you know what their protocol is?
Because opening a phone and looking at the first few texts/emails is faster than imaging. One cannot take a phone and properly image it in the 5-10 minutes they spend with the average phone.