Why? How is it an incovenience? I have it pinned at the top of my start menu...
I'm not taking any chance with it redownloading. I've set it to pause downloading and it can stay that way till hell freezes over...The STO launcher will take care of any patches it needs
Ignoring anything that just comes down to a matter of semantics and personal perference, that doesn't do much to actually answer the question at all.
Is there some specific bug with the Steam client interacting with the Head Start (forcing a redownload of the client), or isn't there? You've got mostly supposition on your end (the bolded part) that it may do it again, not that there's a guarantee that there is an issue.
If that is the problem, you (and anyone else exhibiting this issue) should probably fire off a note to both Cryptic and Steam's support teams, as this shouldn't be happening in the first place.
But, is it a continuing issue or a one-time? That's the big question I have right now (having sat through it once already). If necessary, I'll test it out myself, but I'd love to hear something more solid about this issue.