Aside from the interchangeable flaps, these aren’t that different from the Tenba DNA series. I own the DNA 8, and its a great bag for my E-PM2 and lenses.
What makes a bag ‘mirrorless?’ Really, it’s just the depth. My Olympus Zuiko 14-54 lens, with adapter, might not be much more than DSLR kit lens sized at 4″/10cm, 67mm filter thread, and 500 grams, but it is by far my longest/largest/heaviest lens. When attached to my E-PM2, the entire shebang is about 6-6.5″ deep, depending on whether or not I have the EVF attached. Even that combination is far shorter than most bags designed for DSLRs, which often come in at taller than 10″.
With a bag designed for mirrorless (specifically my DNA 8), I can fit two E-PM2s with primes (sideways), or vertically load one E-PM2 while carrying five lenses (two primes, two zooms, and a pancake), all while maintaining a smaller, lighter, and easier to maneuver package than if I carried a larger bag designed for a DSLR.
Started out doing photography at the age of 6 using an uncle's old 1940 kodak brownie box camera. At 15 years of age, I decided to buy my very own 1975 Praktica SLR camera. I now shoot with a Nikon D850. I do unpaid TFP and commercial paid work.