No. It is hard to argue about this one. That's why both are accepted and that's why it is hard to explain it. Remember the "to je"/"je to" construction that means "this is"/"that is". The "to" in this sentence is close to this one.
You really have to consider when is the sentence likely to be uttered and whether there is or is not a good distinguished form that would be used for "this" specifically. We do not have such a good alternative here. If there were a clear "this" specific alternative, we would not accept "this" for to.
Please understand that it is very different from using "this" and "that" as a demonstrative in front of a noun. Like "this car" and "that car" - "tohle auto" and "to auto", it is really completely different and you can't compare it directly with "to" being used separately.