If using Enum.ThumbnailType.AvatarBust and Enum.ThumbnailSize.Size48x48 together, the returned image from the GetUserThumbnailAsync API will actually be 50x50 and not 48x48! While this is a very small difference in size, it could deeply harm users which are querying specifically sized images to minimise scaling artifacts as the 2 pixel difference deeply reduces image quality. This should be clarified in the documentation as it is certainly not apparent until you actually look into the returned url, the reason why this is the case is because 48x48 is not a valid size for the AvatarBust thumbnail type. (I cannot provide visual-evidence of this in the topic as a recent bug wizard update removed markdown from this category)
Page URL: https://create.roblox.com/docs/reference/engine/classes/Players#GetUserThumbnailAsync