Winglets produce lift, with a vector. The vector direction
can be perpendicular to the winglet surface, fwd or aft.
That is dependant on how it is shaped and mounted.
A lift vector facing the nose (fwd) being called thrust
might be a mishmash of terms, but it happens.
I usually think of thrust as a motive force acting on the vehicle.
Winglet vectors are recovery of lost energy by reshaping flow
to our advantage. Good idea, yes, thrust...... probably not
a really good description of what is happening........

Scott.