Downeaster 20th Anniversary Sale: $10 one-way BON-BRK inclusive

[daybeers]

Surprised this hasn't been posted yet! Great sale for Amtrak's Downeaster, which is celebrating its 20th anniversary this year. The sale is for $20 round-trips anywhere from Boston North (BON) to Brunswick, ME (BRK) January and February with 3-day minimum purchase, but I've found using the code V417 also allows for $10 one-ways. One-way Saver fares from Boston to Brunswick are usually $25.
The Terms & Conditions below say no upgrades are allowed, but does that just mean paying or bidding up to business (usually $40), or does that include upgrade coupons as well? Might just use points as it's a low redemption price.

• Valid for $10 one-way, regular (full) adult rail fare.
  • Please refer to discount code V471 when booking via the Amtrak App.
• For sale December 15, 2021 – February 25, 2022.
• For travel January 1, 2022 – February 28, 2022.
• Valid for travel on Amtrak Downeaster.
• Advance reservations are required a minimum of three (3) days prior to travel.
• Valid for coach seats only; no upgrades permitted.
• Seating is limited.
• Seats may not be available on all trains at all times.
• Fares are subject to availability.
• Offer is not combinable with any other discount offer.
• In addition to the discount restrictions, this offer is also subject to any restrictions, blackouts and refund rules that apply to the type of fare purchased.
• Cancellation fees may apply.
• Routes and schedules are subject to change without notice.
• Once travel has begun no changes to the itinerary are permitted.
• Other restrictions may apply.