I think the difference in talent is probably that deal WITHOUT retention.

I like both players but Kulak is a below average top 4 guy and Tanev is an above average top 4 dman. Under contract or not beyond 23-24.

Not tons out, but maybe CGY keeps the 4th.

If I'm Conroy I tell Holland drop the retention or the 4th. It's a deal.

Kulak would have a tough time making the top 6 in Calgary this year. Who of Weegar, Hanifin, Kylington (if he returns to form), Zadorov would be beat out on the left? If the Flames start the season with:
Weegar - Andersson
Hanifin - Zadorov
Kylington - Tanev

There is no place in that top 6 for Kulak, moving Tanev for Kulak just makes a hole on the right side.

Very unlikely, I think Kulak and the 2nd MIGHT get you Tanev, but without retention and without a 4th coming back.