Almost 2 years since y'all escalated this to the Community Team — apologies for the delay there! But the good news is you now officially only need 3 close votes to close a question on Game Development SE!
After looking at the data, I think it's clear that there's no reason for y'all to have this set at 5. Thank you so much for bearing with us while we got to this request.
We'll check back in with you all in a few months to see how things are going — if things are going great, we may not post an update but please feel free to leave a comment if you want us to post something.
Here's some basic stats of how things look:
Over the last two years, you've had decent numbers when looking into what percentage of questions that received at least one flag or vote to close actually ended up getting closed. While there are some dips here and there, things have been generally in the 70-80% range and the numbers of posts this represents are relatively small (around 50~60 in average in the past year).

The graph below, however, does show something that is a bit more concerning:

When working on this project, Catija had found two primary use cases for this change:
- When too many items are going unhandled (not unclosed, just unhandled)
- When the moderators are doing the bulk of the closing/reopening.
Because the mods here are casting the bulk of the final close votes (which are, actually, mostly the first close votes), the first graph looks good — however, the mods shouldn't be making these decisions on their own, even with other users weighing in. This creates an imbalance between closing and reopening as the mods now have to be really thoughtful about reviewing for reopening.
So, my hope is that changing this to three votes to close/reopen will take some of the workload off the mods and also increase the number of posts that find their way to be reopened - assuming it's worth reopening them!