Mine does it 80% of the time. Has done it from day 1. The compression is so high the engine doesn't freewheel at all. Stops instantly. Accessories don't want to stop (inertia). Hence - chirp. I think its normal and I wouldn't worry about it. I am sure that there are some belts with better friction that may lessen the slip, but unless the noise bothers you.....
The blowby bottle relocation idea is interesting, but seeing as how mine chirped with 25km on the clock, I don't see a buildup of oily residue as a likely cause. My $ . 02
As far as why not all trucks or all the time: ambient temperature difference, temp of belts and pulley, accessories engaged, brand of belt, wear of belt (if its worn enough it may slip without chirping), wear of tensioner spring, differences in engine compression, etc. etc.
Dave