Earlier quoted context omitted.
I am in the "it's not a monopoly" crowd and yes we should definitely use other words to describe companies that do not have exclusive control over a commercial activity.
Exclusive control of an activity isn't needed to be a monopoly. In the 90s, people used Netscape on Macs, but Microsoft got declared a monopoly anyway.
"[...] the U.S. government accused Microsoft of illegally maintaining its monopoly position in the PC market primarily through the legal and technical restrictions it put on the abilities of PC manufacturers (OEMs) and users to uninstall Internet Explorer and use other programs such as Netscape and Java." [0]
"The plaintiffs alleged that Microsoft had abused monopoly power on Intel-based personal computers in its handling of operating system and web browser integration. The issue central to the case was whether Microsoft was allowed to bundle its flagship Internet Explorer (IE) web browser software with its Windows operating system. Bundling them is alleged to have been responsible for Microsoft's victory in the browser wars as every Windows user had a copy of IE." [0]
I do agree that exclusive control may not be needed. However, Microsoft was engaging in other anti-competitive behavior. It's not like they're restricting Windows users to only use GitHub.
[0] https://en.wikipedia.org/wiki/United_States_v._Microsoft_Cor....