I signed up for the strategic 2v2 for three times: 3.18 noon, 3.20 midnight, 3.21 midnight (UDT), with 10 players, 14 players, and 22 players each time. But in all three cases I was assigned with a free win, the possibility of which is 1/5*1/7*1/11=0.2%! This makes me wonder whether this is solely due to chance, or there is some algorithm determining the free win?

Free wins go to spares in matchups. This is most likely due to the greedy matchmaking algorithm, and per the previous thread about matchmaking being bugged Fizzer is working on it (https://www.warzone.com/Forum/536651). I recommend filing a bug report to Fizzer (https://www.warzone.com/ReportBug) to make sure this adversarial case is something he considers when reworking matchmaking.

If I'm right, this is going to happen consistently to your clan as long as you have exactly 1 team join on a template where there is an odd number of participating teams + you have the lowest rating.

Let's look at your time slots to investigate:

https://www.warzone.com/Clans/War?ID=1&Timeslot=12 - 3.18 noon
It assembled 5 teams:
MASTER 1
MASTER 2
Blitz
ONE!
PKU58ers

Then it paired them up, starting from the highest Clan War Rating. We don't know what these clans were rated at the time of matchmaking, but their current ratings are:
MASTER - 144.78
Blitz - 86.34
ONE! - 281.61
PKU58ers - 18.46

So ONE! got paired with MASTER, MASTER got paired with Blitz, and you got a bye because there was no one left. Since no one else from your clan joined the same template at that time slot, your bye turned into a free win!

https://www.warzone.com/Clans/War?ID=1&Timeslot=18 - 3.20 midnight

This time we have teams from more clans, but here they are sorted by (current) Clan War Rating:
MASTER - 144.78
M'Hunters - 176.7
Vikinger - 100.08
CORP - 92.43
TSFH - 58.42
PKU58ers - 18.46
Hodopian Dynasty - 28.25

Odd number of teams. They again get paired from highest to lowest rating. Since you've got the lowest rating, you're the spare. You get the bye, and the free win.

https://www.warzone.com/Clans/War?ID=1&Timeslot=22 - 3.21 midnight
Once again, same exercise.
MASTER (2 teams) - 144.78
FCC - 164.94
SNinja - 69.89
Vikinger - 100.08
Varangian Guard - 26.25
TSFH (3 teams) - 58.42
PKU58ers - 18.46
Hodopian Dynasty - 28.25

11 teams. Odd number. Paired highest from lowest. You've got the lowest rating, you're the spare, you're the bye, you're the free win.

Edited 3/21/2021 04:35:42

Wow, that's impressive analysis. Thanks a million, Kyte! I will report the bug.