To the best of my knowledge, yes, the date of closing, which is the date on which the deed is executed, is the date of sale for tax purposes. Note, however, that at least in the US, the IRS doesn't check what you claim the date of sale is unless you are audited, and I never have been. What would happen in an audit under your hypothetical, I can't say.
> a closing at an attorney's office with delayed recording has the same ambiguity under both systems.
Yes, that's why I asked if such a closing is even allowed under a Torrens system--it seems like it would defeat a key purpose of the system, which is to make sure that the land registry's records always are the "single source of truth" for who owns what.