Water evaporation exposed the meat - is it safe?

Those are interesting temps and times?  I just received my Precision today.  And having already just thawed a 4 lb brisket from our frozen stock of organic side of beef, decided to look up a recipe for brisket.  I only came across one recipe on the Anova web site.  135 deg F for 48 hours, with liquid (pale ale beer) in the bag (in addition to the spices and onions).  

Q1) Why so low for so long when I see you mentioning higher temps at shorter time? 
Q2  Why liquid i the bag, even if it is alcahol?