Participant Criteria – User Testing Lab

We recently ran a user testing lab for our eCommerce mobile app.

Part of the recruitment process for the participants is to make sure they don't work in any type of web based job role (digital marketing, front end dev etc) to avoid bias.

One out of the 10 people observed used language such as 'colour swatch', 'hyperlink', 'expected behavior' as well as bringing up a point about the words 'refine vs filter' and how it takes effort to distinguish between them.. which made me doubt their credentials submitted.

Would I be right in being cautious when taking this persons opinions about the app into consideration or should I embrace the fact they seem to know what they are talking about?

User testing is a relatively new area for me so any information about bias in testing would be appreciated.