yes, truss has been based on / implemented in terms of dtrace since Solaris 10.

(dtrace userland is a library; you can, if you so choose, write your own tooling there. The command is "just a wrapper", a lot of similarities to bpftrace on Linux)

truss(1) is not DTrace-based. It continues to be implemented in terms of the process control and instrumentation facilities provided by the proc(5) file system, as it has been for a long time.

you're right ... "rusty" memory there. You made me check the sources ... it uses libproc but not libdtrace.

(can I be forgiven since I haven't really touched anything Solaris-ish for near 15 years ?)