My experiences (with different situations) were nearly the opposite from those described in the article. My previous company (real estate company with a small s

My experiences (with different situations) were nearly the opposite from those described in the article. My previous company (real estate company with a small software development team in house) hired various outside contractors. One was a company that worked on a mobile app, they invited us into a slack channel and it was effective. It worked well with our workflow as we already used Slack for a large part of our engineering communications. We also communicated with them via email and even some regular old phone conversations. Additionally, we hired a devops engineer who we invited into our slack channel and that was effective. Nearly 100% of our communications with him was in Slack. The devops engineer wasn't someone we communicated with on a daily basis but occasionally we messaged him and it worked fine. We also hired a few engineers through Upwork and invited them into some slack channels in our company and again nearly all our communication occurred through those channels. So, our experience of being invited to another company's Slack as well as inviting outside contractors into our slack channels were both positive. Our work is very different than a marketing firm, so I guess everyone can take these anecdotes with a grain of salt.