Day 1 is deadlifts and stuff (a.k.a. back day)
Day 2 is bench and stuff (a.k.a. chest and shoulders)
Day 3 is squat and stuff (a.k.a. leg day)
Day 4 could be accessory work or "detail work" or "arm day"
That's actually a pretty classic approach. The thing with low frequency work is that you usually need to go balls out when you do train. This program in particular doesn't recommend things like forced reps or beyond failure training, but still, you should be pushing the intensity of every rep you do get to do 100%. Tim Henriques had this good write-up comparing the pros/cons of high and low frequency training: https://www.t-nation.com/training/high-frequency-vs-low-frequency
Also, don't overlook that Bruno suggested 2-3 conditioning workouts to complement the lifting, so it's not like you're only doing those few workouts each week. Depending on your goal, it could definitely be worth giving a shot.
Again, depending on your current goal, that might be the perfect reason to go ahead and try it out.