It's not strict.
The healthy reference diet describes baseline amounts of foods you can eat that are both healthy AND sustainable. But it's not meant to be followed to the letter. It's called a reference diet because it's what you "reference" when you're making high-level choices about what kinds of foods to eat, and how much
Hot take: Use the diet as a guideline for the proportions of different types of foods (meats, starches, veggies, etc) to include in your diet. But you don't need to whip out the gram scale.