Then you would worry about the gears stripping or a shaft shearing.
Seriously, this discussion is good because it illuminates to those who are in need for a new TB what to expect and what to look out for.
I had one timing chain break on me in 49 years of driving and that was on my 1956 Chev six cyl. Fortunately it broke just after I traded it in for a used 1965 SS which turned out to be a pig.
My next was a 1969 MT car of the year, a Plymouth RR, that was a fine vehicle.