Your example is flawed as it implies that a person’s birth year is readily available. How often can you see someone and know which year they’re born? Unless you had them fill up a form which includes birth year and last 4 digits of NRIC, this example isn’t valid.
Instead of making it non-sensitive info, the way forward should be to reduce the info divulged (e.g. three digits without checksum) or protect the birthday to prevent bad actors from obtaining the info thru reverse engineering.
The problem on hand with bizfile isn’t just about whether NRIC is sensitive information. It’s about how easily someone can gain access to these information through a simple search on a webpage that is publicly available. Even if NRIC becomes non-sensitive, it shouldn’t be so easily obtainable via a public portal