Here are the most recent changes to how the ladder works for Sim games... viewtopic.php?f=12&t=1217.

Basically, sim game matching works off rating and uses uncertainty to set the size of the error bars. A player with 1300, 300 stats would sim against any other player with a rating between 1300 and 675, regardless of the 2nd player's uncertainty. If a new player is interested in having a chance to win as opposed to learning something while getting beat down, I can understand a new player with these stats resigning right away if getting matched against someone who was 1300,50... for a sim or anyone game.

A player with 1300, 50 stats would sim against any other player with a rating between 1300 and 1175, regardless of the 2nd player's uncertainty.