More precisely, from the TOS:

> The Site is part of the platform developed and managed by Arduino, which allows users to take part in the discussions on the Arduino forum, the Arduino blog, the Arduino User Group, the Arduino Discord channel, and the Arduino Project Hub, and to access the Arduino main website, subsites, Arduino Cloud, Arduino Courses, Arduino Certifications, Arduino Docs, the Arduino EDU kit sites to release works within the Contributor License Agreement program, and to further develop the Arduino open source ecosystem (collectively, the “Platform”).

> 8.2 User shall not: translate, decompile or reverse-engineer the Platform, or engage in any other activity designed to identify the algorithms and logic of the Platform’s operation, unless expressly allowed by Arduino or by applicable license agreements

So yeah, it seems like the definition of "Platform" is limited only to their hosted services.