Yes, maybe it has to to with timeouts, but I don't think so.
I have tried to look into this, and it seems to me that all the loading of data happens either from the
do_request or
link follow method.
The form find simply parse the received information.
I don't know if tclwebtest runs http 1.0 or 1.1, and as far as I know you can't configure this either.
Sometimes the do_request and link follow methods takes a long time to (but not every time) and this could probably have something to do with timeouts etc.
I think the form find method use so longe time because of several nested regexp. Some of them use up to 1 or 2 seconds to complete but most of them are quite quick. But many small in total add up to a quite long time in the end.