Meso Scale Diagnostics Customer Service Representative interview questions

I went through 4 rounds of interviews over the course of a month. I was excited about the position because I think MSD’s technology is fascinating, so I was constantly refreshing my email waiting for a “next steps” email. I was pretty appalled to say the least when I received my rejection through a Linkedln DM. I found this to be extremely unprofessional. If this is considered acceptable at the company, I likely dodged a bullet. I ended up sending an email to the hiring person and got a response a few days later. Appreciated the response, but the initial let down through a DM was disappointing