They do these types of things, a lot more often than open source projects actually.

Thread Group:

• ARM
• NXP
• Samsung
• Qualcomm
• nest labs (google)
• Apple

I will list more that for example google and/or apple are a part of, but not the involved companies to not make a wall

• OpenID Foundation
• FIDO Alliance
• AOMedia (AV1)
• CSA (formerly ZigBee alliance)
• Bluetooth SIG
• Apache Foundation
• Unicode Consortium
• WiFi alliance
• LLVM Foundation

Not to mention smaller groups that collaborate to discuss strategy over activies like golf or dinners.

The downside is that very very often, the collaboration involves how best to fuck over consumers and the general public for more profit margin.