The Text & Media Block now has a Reading rules option. Turn on "Require employees to confirm they read this content" and an acknowledgement checkbox appears under the content, which the learner has to tick for the read to count. Without it, opening the content is enough:

The confirmation is part of the progress of the content item: the block is only complete once the box is ticked. Content creators decide block by block where a simple read is sufficient and where an explicit declaration is needed.
From "they opened it" to "they confirmed they read it".