Jeff King [off-list ref] writes:

One thing I'd worry about is buffering. One of the nice things about
"-v" is that there is nothing between you and the running programs, so
you are much less likely to be fooled about the order of events in the
output. Or wondering why nothing is happening because real-time output
seems to have stalled. But piping through "cat" may end up with weird
pauses while it fills up a 4k buffer. Using stdbuf could help, but
that's far from portable.

We could pipe to "dd bs=1 conv=fsync" (tongue-in-cheek---I think
conv=fsync is a GNU thing).