After checking the manual again...
Oops, I really should learn to check the manual before writing anything.
There seems to be TREE wireless flash modes. The manual describes them very vaguely:
"Other than HSS modes:
Maximum 1/60 sec
I guess the only difference between those modes is when metering is carried out; during the exposure (OTF-metering) or before it (pre-flash TTL). The guide numbers seem to be identical.
But there's indeed a wireless high speed sync mode I forgot in my previous message:
"HSS: 1/250-1/4000 sec"
The guide number is lower in this mode indicating that it is using pulsed flash.