Yeah, It matters a lot. You need to know they are not going to delete your stuff and that your followers can connect to that relays to download your posts. 

If they are private and your followers can't use them, it doesn't make sense to put there. 

If they are just deleting everything you send because they think you are a spammer, then no one will see what you post. 

Those relays are your home for your posts. Everyone of your followers will connect to them to download what you have to say. If the relay is fucking with them, then they are going to see what the relay wants them to see. 

So, make sure you know what they are doing and you trust these relays.