Yeah, this topic has been well covered and hasn't changed much since the same conversation was had 2 weeks ago.
If I had a dollar for every FFL that threw ignorant, asinine comments out like that... They are empowered by the federal gov't as agents of the state and yet they so often don't know what the hell they are talking about.
It is illegal to install a working telestock or modify the exiting telestock on an M1014/M4, not only because of the AWB, but also because of 18 USC 922(r), which makes it a felony to create or modify an imported firearm into non-importable form. This includes the Benelli M1014/M4. While the AWB may in fact go away, at least for awhile, 922r has no expiration date.
922r was enacted in Nov '90 (it was NOT part of the '89 Bush Ban though it is an epilogue to it) to close the very loophole you are talking about, which is to do whatever you want to the imported gun after it has been imported. Can't do that anymore. 922r stipulates that the imported firearm must remain in a configuration that is itself importable, meaning the faux telestock on the M1014 must stay that way.
The only ways around the 922r issue are these:
1) Replace enough of the Benelli parts with U.S.-made parts so that the Benelli has enough to be considered domestically manufactured and not imported. You will need to replace enough parts so that the sum total is 10 or less imported parts from the recognized list of firearm parts pertaining to that gun. If you look at the master list and cross off parts that simply do not exist on the Benelli (barrel extension, etc.), it is virtually the same as if you added that part to the gun as US made. Get the list down to 10 or less imported parts and you are golden. But good luck doing so.
2) Create an NFA shotgun out of it by submitting an ATF Form 1, an application to create a Short Barreled Shotgun. 922r does not apply to NFA firearms and if you were to legally create an SBS, then after the AWB expires (the AWB still applies to semi-automatic NFA firearms), you can do anything you like to it short of converting it to full-auto.
Benelli would sell these if they could. After all, vendors have been selling telestocks for ARs even with the AWB in effect, leaving up to the end-user to abide by the law because there are legit and legal uses for AR telestocks on pre-ban guns. No, Benelli knows there is no legal way to use these telestocks, so they keep them close and don't sell them as parts or on guns to anyone that isn't a gov't or LE organization.