Lowepro writes on the homepage:

Fastpack BP 250 AW III (Black)
Travel backpack suitable for mirrorless or DSLR camera, 2-3 additional lenses, 13" laptop, 10" tablet and personal items.
Equipment compartment with CradleFit pocket for 13" laptop / 10" tablet
Laptop up to size 27.5 x 2 x 41 cm

According to the Apple homepage, the current 16" MacBook Pro (M3) measures 24.81 x 1.68 x 35.57 cm. So it should actually fit. I can't say how Lowepro comes up with 13".

When measured, the laptop compartment measures approx. 41cm (length or depth) x 27.5cm (width). Unfortunately, I currently only have a 13" MacBook Air.

Hello, yes, my Dell 16" Precision 3571 passes through the rear compartment, which is a through hole, but it's not comfortable, it makes a hard plate against the back, whatever the model.

The rucksack is currently standing next to me in the office - I took a quick measurement. The laptop compartment is 27.5 cm wide.

Yes should fit

No, the compartments in the rucksack are too small for that.