Do you know why ISBNs were designed specifically differently to other barcodes?
It's because you can transpose any two digits and the ISBN will still work. To counter the most simple human error seen when entering book numbers manually.
The same way that you know the code of any ISBN barcode is faulty if it doesn't total up to a multiple of 11 (where any X is taken as 10).
You can design systems to cope with errors. You're literally using probably a hundred different checksum and ECC and error detection systems just putting your post on this page, at every level from your keyboard up to the website's database's multiple storage drives.
If you want a resilient system, you can easily build one where it doesn't matter if people get 5 out of 10 numbers wrong, you would still know where they are. Literally you can choose the number of errors you want to correct and that'll determine the size of the final code and almost all such codes are not prohibitive. We literally use the exact same system to take to Voyager spacecraft where some countless thousands upon thousands of errors can occur in every megabyte of data transmitted and it'll still get through in an understandable way where you know it's correct.
W3W has *SO MANY* flaws that it really shouldn't be taken seriously.
Lat/Long or OS are long-standing, standardised, royalty-free and "just work", and you can do it in a foreign language (I know the German, French and Spanish for the numbers 0-9 without even trying, all I'd need is the compass directions and possible "minus").
But if we want a resilient system, random numbers or letters would actually work far better - even just a small bunch of alphabetical characters could do a better job than W3W, could be transmitted with the NATA phonetic alphabet or Morse Code, and just one or two extra characters would greatly enhance its resiliency in the cases of tranmission or transcription errors.
It's literally an afternoon jaunt for any mathematical student averse in Coding Theory, with a dash of geographical coordinate systems, to code up a solution to all the problems there.
But when Lat/Lon (international, standardised) and OS (UK only, standardised) are staring us in the face, there's really little need to do so. Transmit both. Transmit one and your approximate location. Or just read it twice.
But the problems with W3W go far beyond confusingly similar symbols (not something that Lat/Long or OS suffer from), and it really should be put to bed as anything but a gimmick to get your pizza.