[PKGNG] use more than one threads?

[Alex Keda]

"man xz" say about
 > -T threads, --threads=threads

but, when work
 > pkg create -a

it use only one:
 >   PID USERNAME  THR PRI NICE   SIZE    RES STATE   C   TIME WCPU COMMAND
 > 48672 root        1 103    0   216M   117M CPU2    2  20:39 99.37% 
pkg create -a

how I can use more than one CPU?