Shopify is really no different to any multi-seller platform in regards to how to they deal with accounts. They have all policies in place and it's important to ensure you educate on those policies so you can stay within the trading rules and regulations. As with most of these type of platforms, they can come down very hard on accounts that violate stated policies.
I know a lot of sellers complain when they get jumped on, but it's usually down to the seller ignoring stated polices of the platform and they have the right to shut down the account to protect their own brand.
No matter what supplier you are using, if you're talking about branded products, then always ask for a certificate of authenticity to protect yourself. It's also a good idea to speak to the platform's customer service and tell them the products you are going to be selling and who you will be dealing with in regards to suppliers.
Let them know you have done your due diligence and have certificates of authenticity on the branded products and offer to forward them copies of those up front. If you put everything out on the table up front you will be able to identify any possible issues that you are going to run into and then save yourself before you break any rules.
It's always better to be on the front foot, not just blindly going where you shouldn't go and then getting slammed for it.