Quoting this article which clips this paywalled content — it seems that Microsoft are telling the truth; also it’s interesting to note that Apple locked-out third party kernel modules starting circa 2019.

Further content on the same topic at:

• https://www.welivesecurity.com/2017/05/11/93681/
• https://eugene.kaspersky.com/2017/05/02/at-last-not-all-so-quiet-on-the-antitrust-front/

Microsoft comes under pressure as software suppliers raise market abuse complaints with the European Commission over bundling of Defender security software with Windows.

Security technology suppliers have complained to European Union officials over Microsoft’s alleged abuse of its dominant market position in Europe, according to official EU sources.

A high-level EU official from the European Commission competition directorate said at least three security software companies had “met several times” with the EC to raise alleged market abuses by Microsoft.

The complaints centre on Microsoft’s free security software add-on, Defender, included by default in the Windows 10 operating system. Security companies claim the tactic is shrinking the market for competing security software.