That was a statement made by a pharmaceutical biotech consultant whose scientific background and expertise is unknown. You have to be careful with statements made by someone working within the industry; often, they overstate the advantages of their technology (usually to attract investors).
Animal cells and microorganisms have an advantage in that they can be scaled up and down fairly quickly, and grown in huge tanks. Plants grow very slowly in comparison to cells or even small animals.
I have experience in making proteins in a number of systems, on a small scale for research.
Thanks for the info.