LOL.
That's what they want you to think, but no big ESP such as gmail or yahoo have any set of special rules for Mailchimp or other big guys, because that would open them for lawsuits based on an unfair treatment.
My last company was chained to Sendgrid, until someone with yahoo email account clicked on the "spam" button 147 times... on the same email message! That was in 2015. A glitch in Sendgrid system counted each click as unique, and our spam rate got to be 27%. We got kicked out from Sendgrid faster than we could dispute it, and then they stopped answering our phonecalls.
We moved to Mandrill but that wasn't better because they were super-sensitive. We then built our own Digital Ocean $5 box and gradually start sending emails that were NOT spam. First 50 per hour, next day 100, next week 1000, you get my drift.
Today we email about 2,000,000 opt-in emails per day from the same DO $5 512MB box, built on Centos 6 and postfix. Delivery rate similar like we used to see with Sendgrid/Mandrill, at around 86% with click-tru 55% but that doesn't matter these days.
Bottom line: if you don't send spam then why would you be punished for legitimate emails?? Big ESP will take few weeks (a month?) to learn where to deliver your email and we had nothing but good experience. Of course I don't have to mention basic DKIM/Spif/DMARC other basic stuff alignment. Also bounce mailbox needs to be monitored. If you need any further info/help, shoot me a message I be happy to help.