Is the article proposing that you need an open source FDE solution with deniability? Considering it refers to using Disk Utility as an option if everyone is on MacOS, then I don't think that's what it is going for. It also assumes that these users are using Windows/MacOS, so the need for open source tools doesn't seem to be a primary concern for this organization. I don't personally have a lot of problems with VeraCrypt, but I think most people this article is aimed at would be well served by File Vault and Bit Locker since we have no reasons not to trust those organizations and some reasons to believe they have put their money where their mouth is when it comes to file encryption.

But yes, if what you want is open source FDE with deniability, and cross platform support (not sure why you need cross platform support for FDE) then VeraCrypt is your tool.