Setting aside the merits of the article for a moment ...
Is engagement only posting?
The Office of the U.S. Department of Education says in their glossary that it must be "participating in an online discussion" if you are using it to show attendance. It also says that being there but not academically engaged does not count as attendance. Schools usually take that to mean that participation means posting.
You've got a long uphill battle to convince people that just reading is engaging. This is additionally fostered by a lack of audit information to back that up.
Let's say that I wanted to give students credit for engaging just for reading. Technologically, that is going to be difficult for me to do.
Canvas has a "Mark all as read" command that will show that 100% of the replies have been read. Does that have any validity as to whether the student actually read them? That command can also be invoked after the discussion is over, so you don't know that they did it when they discussion was active or they did it the next day but before the teacher graded it.
At one time, Canvas automatically marked replies as read when viewing with a browser but not with the mobile app. I am not sure if this has been fixed, my testing revealed an error in my code that I need to fix, but I don't have time before I have to leave this morning to get that.
Those last two are generally not available to faculty. The information about what percent of messages a student and which messages they have read or which messages they have liked are available to that student. When you fetch that information, you have to be that student, or masquerade as that student. Most faculty do not have the ability to act as a student.
The access report shows number of times and the last time a student viewed the discussion, but that only helps if the number of views is 1. The data used to make that page contains the first time they viewed it, but people have to go to lengths to get at that information, such as the script I wrote to obtain the access report for the entire class.
There are page views, which may not reflect mobile activity either. You have to be an admin to get access to those and they're not broken up by course, all of the student page views are together.
There are analytics, which sounds like a good place, except that page views, which are similar to the access report and not like the web page views in the last paragraph, are clumped together into the number of page views that happen each hour and not which page views happened. Only participations, which is where the students post or edit, are listed with dates and times.
Reading leaves no accurate trail that can be used for assessing how much time was spent reading.
Time spent isn't necessarily indicative of participation either. I'm a slow reader, but I read very deeply. I may spend hours reading something, pondering, analyzing, and then deciding that what I have to write is either not beneficial, doesn't contribute significantly, or unintentionally upsets people because I tend to be a factual person and don't emote or understand people who do.
Likewise, I don't consider coming to class and reading facebook or doing work for your other classes to be attendance. I lump attendance, participation, and engagement into one thing in my syllabus.
For a discussion, direct engagement can only be measured effectively by posting. If you want to see if they engaged by reading, it needs to be done through another assessment of the student.
I desperately want to tell my students that their grade is not based off what they know, it's based off what they can demonstrate.