Incorrect financial transactions when overriding taxes a backend membership form with buildAmount

In short, here is the context:

• A Canadian association has to charge taxes on memberships, therefore the tax % depends on the billing address of the member (HST in some participating provinces, 5% GST-only for some others).
• We setup a Financial Type "membership" with a tax amount of 99%, because it gets altered later on, and because we want errors to be obvious.
• We use `cdntaxcalculator` to calculate the correct tax % based on the member's billing address. More specific, we are using SymbioTIC's fork: https://github.com/coopsymbiotic/biz.jmaconsulting.cdntaxcalculator/tree/symbiotic

Now go to the CiviCRM backend:

• Assuming there is a membership type, and its Financial Type is associated to a 99% tax account. Let's say that the membership amount is 300$.
• Create a contact record, with a billing address in, for example, Quebec
• Create a membership, using the "simple" priceset (the build-in one)
• The amount of the membership should be "315$" and indicate "includes 15$ tax".
• Click save. All looks good.
• Go to the 'contribution' tab of the contact, click to view the contribution: it will indicate "tax: 297$". That's because in the membership submit function, it reloads the pricesets but does not call the buildAmount hook, so it used a 99% tax rate. The total amount is still good, but the core tax code seems to reverse-recalculate taxes based on the total amount (cringe).