Correct. By the time the question of default init system was being decided by the Technical Committee, the tentacles of systemd were so entrenched that its relative merits or detriments as an init system were of little importance. As Russ Allbery (a committee member) pointed out at the time:

"We’re not really talking about choosing between two competing ecosystems. Rather, we’re talking about whether or not to swap out a core component of an existing integrated ecosystem with a component that we like better."

Also (to try holding back the tide of historical revisionism) let me highlight that Debian's decision was in no way unanimous and the process was not without its own controversy. In reality, the Tech Committee was divided down the middle when it came to their vote on the default init system, and the tie was only decided by the double vote of Bdale Garbee, the chairman of the committee.

GNOME didn't have any significant systemd integration until well after Debian had decided to go ahead with it.

I remember this being a strong supporter, among others: https://lists.debian.org/debian-ctte/2014/01/msg00287.html

Then why did Josselin Mouette, a GNOME packager for Debian, write this in October 2013:

"GNOME in jessie will need systemd as the init system to work with all its features, just like it needs the network configuration to be handled by NetworkManager."