There were no huge problem with reds on photo paper. For example it is a well known fact the Canon reds are the brightest around walking way past Epson K3, and past the Z 3100 in brightness. It was only in the shadows that Epson can not only hold it's ground without the added primaries, but in most cases exceed saturation and chroma.
Measured colors and gamut plots don't tell the whole story. Visually side by sides, the Z 3200 definitely has a more lively red, one that has more local contrast. New inks, a different color map, perhaps some changes in screening all would be reasons why this is so.
Even without comparison samples singularly the Z3200 has reds that pop, purples that are rich and an esthetically more lively rendering of all warm bright tones.
I do have print samples of images on Epson Canon, HP Z3100+3200 here and the differences are easily seen on the right images.
As I have always said, and always been able to prove, most images most of the time will print just as well on any of the three brands.
The entire "reds" issue is and always has been blown out of proportion.
It all started right here on this forum with someone that wanted to print on an el cheapo matte paper, that his Epson 4000 (such a wonderful printer....) could do better.
There seems to be a myth that the with improvements both Canon and HP now with the improved reds will outdo Epson. On most images no, but be careful about a global assumption , as if you look closely Epson still has the advantage of ink pigment loads over Canon and HP and will do wonderful things even on matte papers or your el cheapo papers too for that matter.