Thank you for the discussion @Corby Goade .
I feel like we are biting off big pieces of a complex topic, and I think it would be helpful to focus on either the interests of the property owner or the MTR operator to simplify things,
I think your greater objection to MTR arbitrage lies with why a property owner would want to willlingly enter into the agreement, so I will focus my reply on that.
Pre-internet, being a landlord wasn't easy, but it was straightforward (this is a gross oversimplification). Buy a property, find a tenant, collect rent every month. Fix things as they got broken, and hope for a good tenant. Wait for the equity to increase. Nowadays there are a lot more strategies available to a lot more people, and that has changed the avatars of who is investing in real estate.
Not every investor is defining "success" in the same way. A property owner that is looking to maximize return may want to run their own STR. An investor looking for liquidity may value a REIT. Somewhere in the middle may be an LTR owner who is used to doing the hard work of tenant selection, routine maintenance, and rent collection.
If that owner is used to doing all of that work to receive their monthly rent, would it be appealing to enter into a business-to-business lease with an MTR arbitrage operator? Now, the owner can vet the operator one time, offload routine maintence to the operator, and receive the rent they've agreed to in the lease, possibly for years to come. For many owners, this is a win.
Other owners may value the consistent monthly deposits rather than worrying about the usually seasonal STR incomes.
You mention a traditional STR PM agreement where the upside is shared by both parties. That is a great benefit of that arrangement, but you didn't mention that the downside is assymetrically shared by the property owner. An STR that is poorly managed may leave the PM without his or her portion of the income, but it may set up the owner to lose the property if that cash flow was needed to pay the mortgage. Some owners would prefer a clearly defined floor even at the cost of not rising to the highest ceiling.
While I hate to say it, there are also property owners who lack either the time, knowledge, inclination, or skill to want to manage their property effectively. Perhaps they would make more money if STR was an option, however if that's not permitted in their location, no STR demand exists, or no STR PM is willing to take on their property, they may not have that option. An MTR play may work well for them.
Long story short, it can be logical for a property owner to enter into a deal with an MTR operator. It may not be the best option for you or for many, but it may be a good option for others.