I should have never used the "CH" expression, sorry, because I cannot explain what it is and/or remain a forum member. If you are ever around old mechanics or carpenters, this "hair""measurement means everything.
Think of chain tension like this. The chain will be its tightest when the swing-arm is level. This happens when you sit on the bike, or hit a bump. A bump may make it angles up. Think maximum distance between sprockets.
madmartin mentioned....tight spots. Yes, you are right, but theres no reason to run so tight this becomes a factor. Especially in a new chain like we have here. You should not have any spot significantly different.
For sure , keep it aligned, but its better to run at the maximum amount of up/down play vs the minimum. If you keep it midway-maximum, it will just stay there. You'll adjust at tire changes.
Notice the droop in this chain. Its a dirt bike, so the effect is exaggerated. If this bike were mine, I'd probably loosen the chain, but its very close to correct. Think of his swingarm being level with the ground, and it makes sense. We can get by with less slack than this bike has, but our machines would function just fine with a chain this loose.
http://all-moto-brands.com/wp-content/uploads/2015/03/crf-450-honda-1.jpg