Let's say you are doing a mortgage or any credit card application. You might get an initial approval, but the final decision might be subject to certain conditions. Only when you satisfy those conditions, you will get the 'final' approval. System might generate card numbers or mortgage numbers after the initial approval, and the portal/system you are using for doing that application might show the numbers generated for the product, but it doesn't necessarily mean that you are actually approved for the product you requested, because certain condition might still be pending.
Not really sure how IRCC work internally, so I won't be able to say why COPR number is generated at this stage. From what I know, and understand, the so called 'conditions' are still pending until P2 stage, so I personally wouldn't celebrate until I get my eCOPR.
Again, all of this is my understanding, and could be wrong.