I’d say this is definitely something to clarify during the interview or to ask in the pre-interview stage.
A solid understanding of moulding should be expected from a design graduate but I don’t think employers can expect a young designer to fully understand the intricacies of different moulding materials and processes.
A small but precise plastic part for a CE product will have different requirements, materials and processes than a rotational moulded chair.
Generally, I think that there should be room for lots of on-job training and that you should be allowed to gather experience through projects.
It doesn’t hurt though to read up on that particular employers products and how they generally are made.
If this is a specific requirement for the job, it could be a nice talking point during an interview where you have maybe prepped a few comments and questions regarding process that show that you are interested, know some but not everything and that you are happy to learn.