You are only required to create an account once you reach $30k in revenue. You can always voluntarily register, which you would need to do in this case.
The problem here is that Apple is the retailer and Apple handles all of the tax collection and remission to CRA. Apple wants to have its CRA account tied to your CRA account because of the commissions that Apple charges you.
If you have further questions, I recommend contacting CRA directly. They're usually very helpful. Unfortunately, this kind of business arrangement is actually very unusual as businesses go. But Apple is large enough so that CRA will understand the business from your perspective and should be able to provide assistance.
Unfortunately, the entire process of connecting your CRA account with Apple can take a long time. And since Apple is a US company, there are also IRS forms you'll have to fill out. All of these forms can take some time to fill out - think months, not days.