I agree that a major part of the problem is moving through allied spaces, but also looking at the image, the position of the fighter is not the most advantageous.
the purpose of a choke point is to negate the benefits of greater numbers. when two armies fight in a canyon, there are the same number of soldiers on each side fighting each other, so the if one side has more numbers they don't have an impact in the short term. the best way to use a choke point against an enemy with greater numbers is to stand at the mouth of the choke point, or in front of the door not inside the hall. standing at the mouth enables the negation of enemy numbers and also enhances the effectual number of combatants on your side. the fighter would stand just in front of the door, stopping the enemy from entering the room, but two other less effectual combatants could stand on either side and also damage the front line of the enemy.
now this tactic only works if the enemy actually reaches a bottleneck, where the frontline is in the way of the second rank and they are in the way of the third rank, etc. so with that in mind allies should not be able to move through each others spaces. It makes me think of real world bottleneck situations. back when I was a kid going trick or treating, there would be a line up to the front door of a persons house, usually with a garage on one side, and bushes or something else on the other, so once we got our candy it was extremely difficult to retreat past the other people in line. it was just all one big jumble where we were caught on each others clothes and some of us didn't exit the doorway area until everyone behind us had already left. now applying that to melee combat, I wouldn't want to even try that because it would be extremely easy for someone to attack us while trying to get past each other and we couldn't defend ourselves.
the purpose of a choke point is to negate the benefits of greater numbers. when two armies fight in a canyon, there are the same number of soldiers on each side fighting each other, so the if one side has more numbers they don't have an impact in the short term. the best way to use a choke point against an enemy with greater numbers is to stand at the mouth of the choke point, or in front of the door not inside the hall. standing at the mouth enables the negation of enemy numbers and also enhances the effectual number of combatants on your side. the fighter would stand just in front of the door, stopping the enemy from entering the room, but two other less effectual combatants could stand on either side and also damage the front line of the enemy.
now this tactic only works if the enemy actually reaches a bottleneck, where the frontline is in the way of the second rank and they are in the way of the third rank, etc. so with that in mind allies should not be able to move through each others spaces. It makes me think of real world bottleneck situations. back when I was a kid going trick or treating, there would be a line up to the front door of a persons house, usually with a garage on one side, and bushes or something else on the other, so once we got our candy it was extremely difficult to retreat past the other people in line. it was just all one big jumble where we were caught on each others clothes and some of us didn't exit the doorway area until everyone behind us had already left. now applying that to melee combat, I wouldn't want to even try that because it would be extremely easy for someone to attack us while trying to get past each other and we couldn't defend ourselves.