I'm gonna say no, its not unsuitable. Extra chainstay length gives you a) better clearances for tyres and mudguards usually and b) more stability. The bike will feel a bit less chuckable under you but will be more stable and predictable which is handy for carrying luggage.
A bike can feel a bit unwieldy if the weight of the rear luggage is further back than the rear axle which can be necessary for heel clearance on short frames whereas it can be further forward on a longer rear end.
I'm gonna say no, its not unsuitable. Extra chainstay length gives you a) better clearances for tyres and mudguards usually and b) more stability. The bike will feel a bit less chuckable under you but will be more stable and predictable which is handy for carrying luggage.
A bike can feel a bit unwieldy if the weight of the rear luggage is further back than the rear axle which can be necessary for heel clearance on short frames whereas it can be further forward on a longer rear end.
BUT, you can ride just fine on a shorter bike