The plot thickens...
Callaway 33, R11 irons June 2014
Callaway Soft L33, R11 irons, August 2015
I tried it again tonight with the R11 irons and found no difference from the test that I did 14 months ago. To rule out a cache quirk or a stealth update by WGT in the past day I reloaded the Nike 97 irons again and got the same results that I got yesterday...still shorter with those clubs now than in 2014.
I'm beginning to think that there's a chance that I loaded the wrong balls for the L97 test in 2014. I had both L43 Cally Legends and L37 i(z)s in my bag, and both are longer balls than the L33s. The other explanation is that the Nike 97s, not the Callaways, have changed.