This is why I ALWAYS tell people not to trust what their agent tells them about esoteric insurance coverage questions and to ALWAYS get the answer from an underwriter.
The agent is doing his/her best, but their opinion on coverage is not binding on the insurance company. If an agent tells you X and that turns out not to be true, its not the Company's mistake and you are left with suing the agent's Errors & Omissions (malpractice) policy to recover the damages they said you were covered from. Not an ideal situation at all. And if the argument comes forward that the agent is a representative of the carrier and thus the carrier is bound by the agent's word on the matter, this is generally not upheld in court, except when the 'agent' is actually an employee of a direct writer like GEICO. For an independent agent... your only recourse is the E&O policy and a lawsuit against your agent.
In this case it sounds as if the insurance company is making a genuine attempt to make this right and keep the agent from having to eat crow. After all, an endorsement was written and premium was paid, but I bet what happened was they were not contemplating the 'e' in ebike when the company created the endorsement that the agent used, and they want to try and actually do the customer right.
I am a licensed agent in Michigan and done quite a bit of work there on policy language and especially with their very extensive PIP reforms and MCCA changes...
@California Flash I suspect you know that if this was pre-MCCA reform of like a year ago you would be charged the full MCCA fee of over $200 in addition to the actual insurance cost. You formerly did not have the option to reject medical to get out of the MCCA charge, or what is now known as the MCCA Deficit charge that is (for now) $0.
By the way, something few Michigan consumers take advantage of is dropping their PIP from Unlimited to any lower number, which can be as high as $500,000. Doing so saves you $100 per vehicle as when you take ANY of the lower limits, you become exempt from the $100 (this year) MCCA fee. Of course, look at all of your coverages carefully before selecting a lower limit... but the rest of the USA gets by just fine with lesser limits.
Writing a bicycle on an auto policy as a moped is problematic at best. I would look at your policy VERY carefully to see how 'moped' is defined and ensure your bike actually fits the definition. However... I have to say the price they are charging you is more than competitive. BUT as you noted, the policy uses either Actual Cash Value or Stated Value and both involve depreciation. The benefit of a Markel/dedicated bicycle policy from Velosurance is they don't take advantage of the escape clause in Stated Value and instead treat it as an Agreed Value. Something to consider.