I am not aware of any sources that require a pilot study as mandatory in qualitative interviewing. Indeed, there is an old saying that if you first interview works, then it is data; if not, then it was a pretest.
Piloting is not mandatory, although you can pilot your interview guide to be sure that your questions are clear and unambiguous. Also, when your interview is going to be in another language, you may need to translate the questions and pilot the tool.
IMO, pilot study is not mandatory but is a blessing. It helps in anticipating difficulties or addresses serious problems that might occur in the field study.
If you decide to do your field study without first conducting a pilot study for your research, and later on you are taken to task, then you need to be able to defend your decision and provide justifications from very thorough literature review to support your decision.