Yes it’s more about nutritional quality reducing and taste as well. Degradation of vitamins and minerals. In the RTD there may be some reductions in physical stability - i.e. it may separate. With both it’s more this rather than safety however if you choose to consume Huel past it’s Best Before date you do so at your own risk (without trying to sound too extreme!), there may be some risk of spoilage.
What’s the context? Have you got some going past it’s best before?