Only half thought out reason I can come out with is balancing between the races for hunting and digging.
Lets look at matis - risky to get to 200 zones (Hidden source is desert xp so ignore that) Heretics hovel does not work but Bog does. The 250 zone tps work.
Lets look at Zorai - easy to get to 200 zones from cities and the 250 zone tps dont work.
Lets look at Fyros - Citys are both in 200 zones and the 250 zone tps dont work.
Tryker I really cant say as I haven't been into Fount and Enchanted Isle but all that water does add a certain level of safety so I would expect those TPs to be not working.
Roots All working that i've found except the nexus. However since nexus is forest and not pr experience I can see why.
Its only a theory so plz dont flame