Hi,
Sorry, but this is going the wrong direction.
First, Google defines the use and benefits of "nofollow" attributes (just like other attributes ) very clearly: see
developers.google.com/search/docs/advanc...alify-outbound-links
and elsewhere.
So, yes, "wrong" use, e.g. for site-internal links, can affect ranking negatively, and if only because you're basically attempting to "hide" potentially valuable content from search bots.
And that's it. So, the section in the French article is taken out of context, and both the <a> tag as well as the "nofollow" attribute are making perfectly good sense for the add-to-cart button -- for the reasons as mentioned by Nicolas here above, as well as it enables site owners and users to pass on simple add-to-cart links per email, messengers, etc.
Please leave the <a> tag as is. Or, at the very least, give us the option for utilising <a> tags for the purpose like in older HikaShop versions.
Merci beaucoup!
EDIT:
Sorry, forgot to mention: the only downside of the <a> tag I can think of is that not all bots respect the "nofollow", eventually leading to "bad bots" causing fewer or more carts being generated. But even that is not a problem as HikaShop gives us -- thankfully -- the option of unused carts being auto-deleted after X days. So, nothing to worry about there, either.