From the article:
> The 11-digit codes [...] are hard to memorise and a single mistyped digit would send a courier to the wrong address.
The plus codes FAQ [1] mentions that they thought checksums weren't important for a couple of reasons:
* Not needed for codes that are copy pasted rather than typed or written
* Mistyped codes will be "obviously wrong" due to referring to an unrelated area
I'm not too convinced by the rationale, as playing around on Google Maps shows a typo of one digit can at least sometimes produce another valid code not too far away. And even if typoed codes were always obviously wrong, it's not clear that a computer would recognize incorrect but valid codes as well as a human.
[1]
https://github.com/google/open-location-code/blob/master/FAQ...