From what I can tell, it's written in Electron. I assume they did this so that they could share the code base between desktop (win/mac), ios/android/winphone, and web -- keeping the features sets the same on all platforms. VS Code is the same way and that works beautifully on Mac. I expect that same for this.
Disclaimer: I work for Microsoft (Azure) but have no relation to Office or Microsoft Teams.
It is not about the technology platform. You still have to dedicate resources to ensure feature parity across both OS systems. When MS starts selling Teams to huge enterprise customers (e.g., Walmart, Ford, GM etc.) that are on 99% Windows platform and the feature request and pressure starts building, where do you think the resources would go ? It is not MS fault, it is the nature of their business. Windows based enterprises are their bread and butter and that's what they will prioritize. I work for an enterprise Cloud company, and we prioritize IE because of this reason.
> It is not about the technology platform. You still have to dedicate resources to ensure feature parity across both OS systems
It is about the technology platform, because the amount of resources necessary to ensure feature parity is a function of the platfrom. Word for Windows and Word for Mac are probably two separate giant monsters of early-90's C++ and keeping them in sync is agony. Assuming Teams is written in Electron, the amount of work is nowhere near the same; not having feature parity across operating systems is probably harder than having it.
Disclaimer: I work for Microsoft (Azure) but have no relation to Office or Microsoft Teams.