So the bug is simple vs your text on secondary objective.
You state “win without Summoning Creatures with Lifelink”
SOOOOOO
A creature is SUMMONED and does not have lifelink, but a support on the battlefield give that creature lifelink that is contrary to your statement above because it enters without and is given…
Well your objective tags it as a summoned creature with Lifelink.
I reported this issue way back when Avacyn’s Madness ran. There is also an encounter with this objective. I think it’s the Watcher in the Web encounter, not entirely sure. I used the Sphinx token support with Cartouche of Ambition, which also counted my Sphinx tokens as having lifelink.
In Avacyn’s Madness (node 2-2), There’re no creatures with defenders in my deck but I lost objective when I summoned or enhanced the creatures that got defenders with “Arixmethes, Slumbering Isle”.