My view is that your old account will probably contain enough information to ID you “as an individual”. May not be forensically 100% but good enough for data brokers to trade your data as, say, “98% known individual” if that were the spec for good enough for cost effective targeted advertising.
If however one used an account where account details were inaccurate then any targeting may be less useful but your “fingerprint” is perhaps regarded as enhanced by brokers.
This goes hand in hand with the privacy of apps installed. If one picks privacy friendly apps there is not so much to leak back via Google in addition to the initial install. Apps on the other hand which love to share are given a helping hand with your ID / footprint with a registered account.
App Lounge does have to identify the device (in order to do business with the remote server) even though anonymised. The addition of the account will undo anonymity.