I think this is for the recent surge of quasi-open-source license changes some products have gone through. That's why they underline the difference between free software and open source.
Recently people started saying that the OSI's Open Source Definition is restrictive and obsolete, that having the sources available is enough, that it's not a problem to restrict usage, etc... That's why it's important to stress "free as in freedom" in free software and not "open as in you can see the source" in open source.
No it wouldn't, for software to be "Free software" it must be GPL-or-other-copyleft-license licensed, which aside from being trivially impossible in a world without intellectual property laws, also has different outcomes than placing the source in the public domain. For example nothing prevents me from taking some public domain code and including it in my closed-source application, but the GPL forbids this.
No, for free software to be "Free Software" it must respect the Four Freedoms (https://www.gnu.org/philosophy/free-sw.en.html). GPL-or-other-copyleft-license happens to respect them, but so do the Apache, BSDs, MIT and other licenses which are not copyleft.
Recently people started saying that the OSI's Open Source Definition is restrictive and obsolete, that having the sources available is enough, that it's not a problem to restrict usage, etc... That's why it's important to stress "free as in freedom" in free software and not "open as in you can see the source" in open source.