Stax tonearm idiosyncracy

I recently acquired a 9-inch Stax tonearm as part of a turntable deal. It's got an S-shaped arm tube that is joined to the pivot via a connection much like that which is used to attach the headshell to the other end of the tube. But at the joint near the pivot, the arm tube is "floppy". It does not make a rigid connection to the pivot point. The seller tells me this is normal. I find it hard to believe, but I am looking for comments from anyone who has ever used one of these. Thanks.
Strangely, it probably is normal. I had one briefly and I recall that idiosyncrasy.

A college buddy of mine had one then and I remember the same thing.
How the heck can it work properly? The arm tube can go all over the place in the lateral plane with respect to the intended pivot point.
Dear Lewm: You are right.

I own an Stax one and there are no single " movement " at that tonearm joint, at least in mine.

Regards and enjoy the music.
Thanks, Raul. I thought I was losing my mind here. There's a little set screw on the underside of the tonearm, where the arm tube joins the pivot (this is the joint that is "floppy"). Perhaps by tightening that set screw the joint will straighten and become stiff, if you will pardon the expression. (Sorry, could not resist.)
Dear lewm: Yes, that its work.

regards and enjoy the music.