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The subject of intentional breeding or meat rabbits is prohibited. The answers provided on this board are for general guideline purposes only. The information is not intended to diagnose or treat your pet. It is your responsibility to assess the information being given and seek professional advice/second opinion from your veterinarian and/or qualified behaviorist.
@Daisy No worries about that, no offence taken 
Oxbow’s website says:
“Always choose an age-appropriate pellet formulated specifically for rabbits. Oxbow’s Essentials Young Rabbit Food is ideal for rabbits under one year of age. For adult rabbits, choose from one of Oxbow’s three premium adult rabbit formulas.”
This implies that adult rabbits should be getting a different kind of pellet. Of course one could argue that ultimately as a corporation they would still push for their own products, but since Oxbow is such an established brand and they have proven to be a reliable one when it comes to rabbit care, most of the time I take their words at face value.
I’m not a vet or professional bunny expert so I don’t know for sure, but I think in general the main reason why people say alfalfa is bad for adult bunnies is because the main ingredient (alfalfa meal) is too rich and can cause an adult bunny to become overweight. The extra calcium in alfalfa can also cause chalky pee, and there’s been quite a number of members here who managed to resolve the chalky pee issue by simply switching over to timothy based pellets. Technically decreasing the pellet amount should resolve this, but doing this would mean decreasing all the other nutrients (besides the fattening ingredients) found in the pellets too, potentially causing an imbalance in the overall diet and a lack of other nutrients, because pellets are made out of so many different ingredients.
Compared to a timothy based pellet for example, the bunny can enjoy a normal, limited amount of pellets and still get its daily amount of necessary nutrients without compromising due to a certain “extremely fattening” ingredient, if you know what I mean.