I would think that the size of a clubs playing squad could be taken into consideration regarding "wanting" to play a game or not.
Also the availability of a clubs star players.....if injured then a postponement might be advantages to a club to postpone that game till later.
Also clubs going through a poor spell of results might prefer to "put a game off" till later in the season.
You've hit the nail on the head there with your middle paragraph.. Clubs want to postpone based on who is unavailable rather than how many. I say tough luck, get them vaccinated and have good procedures.