Many others, especially in recent years, have been proposed and created by Guest Editors.
The way I run special issues with guest editors is different from what I have heard other journals do because I maintain control over the review and decision process. I have heard that at least some other journals turn that role completely over to the guest editor(s).
What I have the guest editors do is (1) to review papers before they are submitted to filter out those that will clearly not survive the review process or are for other reasons not suited to the special issue, and (2) to recommend potential reviewers to me.
Eventually, each paper will have one reviewer who is a guest editor, plus to other reviewers. All three of these are anonymous to the paper authors. I pay a lot of attention to the reviews of the guest editor. If the guest editor recommends rejection, and the other reviewers are largely in agreement ("rejection" or "major revisions"), then I will reject the paper.
If, however, the other reviewers recommend rejection, but the guest editor does not, then I will carefully conciser the guest editor's comments and I might contact the guest editor and discuss the issue, if that seems appropriate, before I make the final decision. On the other hand, if the other reviewers have convincing arguments, then I will reject the paper without contacting the guest editor beforehand.
Full acceptance of a paper requires acceptance by all three of the reviewers. This is the same as the process for all papers submitted to TG. (Sometimes one reviewer will recommend rejection after the first round of reviews and decline to review additional revisions. If the other two reviewers favor revisions, then I will return the paper to the author(s) to revise it, but seek an new third reviewer on the next round of anonymous reviews.)
In sum, special issue papers are somewhat less likely to be rejected than non-special issue papers submitted to TG, but must still meet the same requirements to be accepted as other papers do. Also, reviewers tend to be somewhat more lenient toward special issue papers (though not always), which can gives those papers some advantage. And finally, even though guest editors are not in full control of accepting or rejecting a paper, they have a lot of influence.