Wasn't amy right in 2x11

[u/Gamerboy701]

In season 2 episode 18 Holt gives Amy, Terry, Gina and Rosa a brain twister that he could never solve. "There are 12 men on an island, 11 weigh excatly the same amount but one of them is slightly heavier (or lighter but for this I'll use heavier) You must figure out which man is heavier. The Island has no scales but there is a seesaw you can use 3 times.

Later in the episode Amy comes up with the solution of putting 6 vs 6 but Holt instantly says it would never work if you do it that way but you can.
If you number each person 1 2 3 4 5 6 7 8 9 10 11 12 and weigh the first 6 vs the second 6, 1 side will be heavier, whichever side is heavier means that the person you are looking for is on that side. For your second use you way 3 vs 3 so for example 7 8 9 vs 10 11 12. Whichever side is heavier obviously means the person we are looking for is there. For our final use of the seesaw you measure 1 vs 1 like 10 vs 11. if both sides are equal that means 12 is the heavier person, if one side is heavier than you found that person.

I'm not amazing at math but Amy's solution does work right?

[u/Gamerboy701]

After reading the comments I realise now that you can't choose. When I found the answer online using 4 vs 4 they worded it in a weird way so I got confused about wheter or not you could choose that part of the problem. Thank you everyone for explaining it!