If I were in your shoes, I would probably mention the change in tone/word choice to the lead on the project since you have a good relationship with them. Just mentioning that you noticed the change and aren’t sure about it doesn’t need to be combative, and I would be truly shocked if it cost you the job. Depending on your state it might even be illegal to fire you for something like that.
I personally would not take a stand or refuse to do the voiceover or anything like that. I would make it clear that I would do the voiceover using the script as it is written. I would think of it as providing feedback rather than making demands, which seems like it would be within the purview of a QA reviewer.
This way you can at the very least get more information about the situation - find out whether this was an intentional change. If so, it may be time to start making moves so you can eventually drop this company.
IIRC the reason most caps used to be unrecyclable (many still are) is that they had a liner in them made of a different material. Because such caps were composite materials (using different types of plastic for the liner and the cap), they would make an impure product if recycled. The same problem applies if the cap and bottle are different types of plastic, which used to be more common.