Usually when you start the process you have to provide more details on whether the role was paid etc. They will make a decision as whether to seek a reference or not based on their experiences - they literally request these types of references day in day out and so know what is likely to be obtained and what won't. They will speak to you if they have any concerns or want you to provide any further information instead.
In all honesty, yes it is slightly weird to ask this. You are not going to lose a TC for an honest mistake that can be explained.
