Yeah... I'm not too keen on this idea.
The purpose of homework isn't just to give homework. It's a two pronged resource. It gives students the ability to practice methods learned in an environment in which is supposed to exemplify individual study habits. It gives educators the data they need for lesson modification and intervention signs. If 9/10 students got 80% or higher then mastery was achieved and that there must be an intervention in place for that one student to help them understand that concept. You don't want to wait until the test to know that this student needs help. But if all 10 students got mixed results on the homework ranging from 40-90% correct then that educator must reteach that lesson and teach it in another way. Again you don't want to wait until the test or a major assessment to find out this data.
Futhermore reading doesn't solve everything. If a student is struggling in math then reading isn't helping that situation. Neither for other aspects as writing skills, scientific thinking and analysis as well as hands on project based learning. Furthermore from an educator's standpoint: Let's say you only have a 40 minute math block. With no homework or additional reinforcement, that student isn't going to touch another math concept until the next day. So for those who understood the concept in that 40 minutes great, for those who half way understood still have a lack or clarity or practice at that concept and more importantly they did not have a chance at learning that subject WITHOUT guided practice. This handicaps what the student can do on their own which is the most important aspect because of standardized testing.
And look, let's be real. Simply saying read 20 minutes a day isn't going to be a totally accurate representation. Reading logs can be falsified. Parent involvement can be extremely low. Even with assessments tied to reading assignments, those can either be cheated with group communication or services like Sparknotes or completely skipped altogether by students. With the many distractions kids have in this modern age I don't feel like this is the best way to go about this.