Exactly. Only an engineer would care about that distinction and I agree the article is at fault for calling it out as it does.

Upload literally means send (to a machine). Download means receive. There is no confusion there!

When you "share" something on a blog, or on social media, you are in fact, uploading data to that server! When I had a blog (in the early 2000s) I didn't bother to implement a back-end, so to share an article, I had to upload it. These are implementation details that should be, and fortunately now usually are, transparent to the end user.

The concept of sharing is far too nebulous and some icons get caught up on the future state the of the data. The concept of lots of people (implying sharing with a group, which isn't relevant if you are only sharing it with a single person); or the idea of "sharing a conversation" which implies a two-way exchange (hence the icons featuring loops) but again, that's something that might come later.

However, clicking the icon does not equate with sharing in that sense. It performs one specific action: one part of the sequence that makes up a conversation. It is only the sending/posting/uploading part. Perhaps even "speaking" or "telling". All of these words are equally synonymous in terms of what will happen, right now, as a result of clicking (or tapping) that icon. And that is the only context that matters.

Apple gets this right by focusing on the context of the immediate action, which after all is what the icon is supposed to represent. In this case, that action is that the data will be sent somewhere. There is a further sub-menu of options for all the possible destinations, which can be more explicit about what each one will do (e.g., send to one person, send to group, make public).

Some of the other icons might make sense at the second stage, where there is a need to distinguish between these different kinds of sending. In that context, icons alone are not ideal because there are too many options, yet lack of screen space isn't the problem anymore. Explicit text is better in that case, which is what OSX and iOS both do.

The Windows (Ubuntu) icon for example (or any of the other "group of people" icons) would make a lot more sense if it were a toggle, where selected means "this is public" and not selected means "this is private" but that's not how it is used (and there are also better ways to represent that).

The word "share" also isn't typically associated with an action that can be undone, like toggling a visibility property, even though (from a technical rather than marketing perspective) that is the only sense in which "sharing" is ever different from plain old sending.