Hola Marcos

Yes, we limited the use of mucho here to the masculine form as this is what seems to be the confusion in students when using muy and mucho. We don't go into detail here on the different forms of mucho - the idea here is to distinguish between "very" and "a lot" in Spanish. We refer to students to the more detailed lesson in the TIP part, so they can see the agreement. 

For any feminine noun you need mucha, muchas:

El guiso lleva mucha sal.

Comiste mucha coliflor.

He comido muchas patatas.

Saludos