What you say is technically correct, but you miss one big point about rule 33; it was made for precisely this situation. Therefore, it compelled the committee to use the rule when the very situation it was designed for comes up, even though, as you say, technically a DQ was avalable too.
The committee was not compelled to invoke rule 33, and remove the penalty for violation of rule 6-6d, which is DQ.
It was an option for them. They took it.
They could easily have decided that the violation of rule 26 was egregious enough to warrant the DQ for trying to get away with it. Tiger should have know better (it is his responsibility) than to violate rule 26, and even inexperienced players know they have several options to avoid a violation when they are uncertain about how to proceed. (play another ball you know is safe, or ask for a ruling.)