Yes, it’s true. Seven “that’s” may follow each other, and make sense:
For be it known that we may safely write
Or say that “that that” that that man wrote was right;
Nay, e’en that that that, that “that THAT” has followed,
Through six repeats, the grammar’s rule has hallowed;
And that that that that that “that THAT” began
Repeated seven times is right, deny’t who can.
My Lords (says he) with humble Submission,
That that I say is this; that That that, that gentleman has advanced is not That, that he should have proved to your Lordships.
~Spectator, No. 80
And that’s that!