Yes - airline ground staff never question me when it comes to items strapped to the outside of my backpack.

I have a Patagonia Snowdrifter when I love because it has external straps on all 3x sides plus a cross-shoulder strap. I put a yoga mat on the front, large lumbar pillow on the side, and water bottle on the other side. A fleece jacket can go on the cross-shoulder area so it's basically behind your neck. It's basically another 15L worth of items strapped to a 30L backpack - never hear a peep from gate agents (including international locations) when I walk onboard with backpack plus hardside spinner.