This is just false. You can opt to keep e.g. a hash to check against future additions. Else you also would not be able to comply with the 12 month requirement.
Personal profiles are messy. People have different names, addresses, email, phone numbers, and different people sharing any of the aforementioned details. This is complicated enough with the raw data and unless you have a very simple profiles or opt-out rules, such as treating the entire household as one, you're going to need more than a simple hash to figure out if there is existing opt-out history.
Profiles may also need to be kept for transactional purposes. Presumably, data brokers and people who have only heard of you through brokers wouldn't have any transactional activity. But everyone else likely needs to deal with opt-outs on the distribution side, making opt-outs a solved problem that doesn't need to happen on intake.
So...sure, you can.
But I wouldn't hold your breath that this will be seen as a reasonable expectation for most developers or businesses to implement.