Officially the position at TEMCO is that their wire is annealed. My direct supplies have been remarkably consistent though and I stopped checking wire lengths quite some time ago. However, as I posted just a bit earlier, TEMCO supplies tendered through eBay (by them, at discount) often reflect weaknesses (thickness variations) which have made it much more prone to breakage with simple hand tension. This suggests off-spec production whatever the cause or preparation.
Other sources and brands have not filled me with an abundance of joy.or confidence. And I was testing wire for some time.
My consideration is that any annealing or
force applied to the wire potentially can weaken it or thin it impacting its resistance as you suggest or contaminating it's surface. All these just making the results of oxidizing it for our needs less predictable. So a few pennies more are well spent I believe to ensure good and predictable spec wire.
Surprised somebody hasn't undertaken the QC on this here at ECF. My Fluke and I involuntarily parted company some time ago.
Good luck.