This thread is almost over and everyone will go home without anyones
mind being changed. But I will put in my bit anyway.

I think making a mechanical connection before soldering is usually a
good thing. Not because it is needed after the joint is soldered, but
because it prevents any movement while the joint is cooling. You all
have seen the frosty look of a joint that was moved as the solder
solidified. So I agree with Jim that a mechanical joint is not
necessary, but it may prevent a " cold ' solder joint.

And then I agree with Carl too. A solder joint is only so strong. If
it is being mechanically stressed very much it will fail.
But if the solder is only supporting a short bit of wire, the stress
will be well below the yield point of the solder, and you won't have
any fatigue problems.

And I think the reason you should not tin stranded wires being held by
screws, is not so much that solder cold flows, but you do have thermal
changes to contend with.
You get the solder deforming when there is expansion, and then oxygen
can get in when there is contraction.

Dan