You are referring to very old threads, and lots has changed since then, most importantly the addition of Simbrief integration.
The number of containers, if the airplane is not cargo, is no longer based on "just" the passengers number / 220 lbs, as it always was. This approach had issues, because it couldn't account large and small airplanes at the same time, or with combi configurations, resulting in either big airplanes always using the max amount of loaders even if they were half empty, or small planes never using the max amount of loaders even if they were almost full.
The current method is more realistic, because instead of using the passengers number as an absolute value, it will calculate a fill up ratio based on the actual number of passengers against the Maximum amount of passengers that airplane can carry, adjusting the number of loaders/containers in proportion to that ratio so, no matter how large the airplane is, the number of loaders/containers would always be variable to give an idea of how "full" the airplane is, no matter its size.
The issue is, the "Max amount of passengers" is not a data we have from the sim. But we DO get it from Simbrief, so we use it if we have it. This means, if you use Simbrief, GSX will be able to calculate this loading ratio, which is valid regardless if the number of passengers was read from Simbrief or typed manually.
If you don't use Simbrief, the number of loaders will be based on Payload, which means the actual Payload at the time you called Boarding. This is also changed and improved, because it's not a straight Payload / 220 lbs as before, but it's again a ratio between the maximum payload and the actual payload. The difference here is we don't need Simbrief to calculate the ratio, it's made using this formulas:
Max Payload = Max Gross Weight - Fuel Weight - Empty Weight
Actual Payload = Total Weight - Fuel Weight - Empty Weight
Here, not using Simbrief means the actual payload depends on what the payload was when you called GSX boarding so, if you called it with the plane empty, you'll always see 1 cart. However, if you DO use Simbrief, the actual payload will be calculated using the PLANNED payload, so it wouldn't depend on the airplane load at the time you called Boarding.