It is unlikely that this "trick" will work as the systems are getting smarter and smarter around this, plus its built into the T&Cs to not allow. So the chances are high that you are just building yourself hassle of checking in/out, or at least going to the front desk (though you can try). With this particular promo, if you are traveling with someone then having their name/Marriott number on the second reservation would achieve the same outcome though - as you'd get the bonus promo points split to each of you for a stay, which you can then transfer between each other for free (up to a limited number of points each year), plus the added benefit that could give you extra stays to try and get your points later. For 2025 Marriott points it may be a level of hassle beyond what you want though, amplified if you have different status levels.

Instead if this is important to you then you need to cross the street and try a different Marriott branded property in the same city/district - sometimes they are even in the same shared building.