your attorney is not wrong, assuming you can get I-94...

As Canadian, you don't need a H1B VISA, but a new H1B status i.e. I-94 when entering to US. don't mix them together.

AP is just a backup in case you get rejected for H1B I-94.

Never ever enter US just using your Canadian passport and citizenship only, without either H1B or AP, which will result in giving up your 485.

Be tactful. Just my 2 cents.