*This only applies to their starting lifestyle for adventurer league play. For a home game you can let them start with whatever they want. It's important to remember that adventurer's league is a specific interpretation of the rules for organized play.
More importantly though, this gets at how downtime works in Adv League. Downtime days in Adv League work as a specific form of currency. When you complete a part of an adventure you get 10 days. To spend those days you pay a specific amount (the living expenses for your desired lifestyle level). (ALPG 5,6)
"Practicing a Profession" is a specific way to spend your downtime. Using it this way doesn't cost you anything, and normally a character in town can do this at a comfortable lifestyle (if trained in performance and you choose to use it, you can do so at wealthy). However, there is another option for this particular item. (PHB 187)
When you spend time "practicing a profession" and want to do so in the wilderness, you can do it and be considered poor. If you are trained in survival you can do it and be considered comfortable. However, neither of these things have anything to do with the starting lifestyle of someone trained in survival. (PHB 159)
It's also important to note that those are the default starting lifestyle expenses. You are free to go up or down if you want. If you wan to go down a level, simply spend a day paying at the lower level. If you want to go up a level, spend 30 days paying at the higher level. For whatever reason, they have decided that the Outlander should start at poor, this is obviously not respective of the fact that the background comes with training in survival, but merely a decision made by WOTC's organized play team.