If this is anything like IKEA flat pack furnishings, you want to retain access to tighten the screw joins over time, IKEA recommends after a couple weeks use, then at intervals over the years of use
I’ve an old IKEA nightstand (pine) that’s served as an aquarium stand for many years, holding a 12gal Eclipse (that should age it
this AIO tank has been discontinued for 10 years or more ) and more recently an ADA 45P and currently a Flex 34, the drawer and door still open/close perfectly so there’s been no shifting/warping of the frame despite its far from intended use
I’d guess your stand is pressboard (or similar) with laminate (veneer) - and water resistant but susceptible to standing water (or slow leak damage)
With care it should serve many years
Re the cutout area, a framed aquarium would manage just fine - and going by the US WaterHome AIO rimless aquariums, so should most rimless (someone undoubtedly has done the physics)
BUT
many rimless aquariums will state in the fine print, that a solid surface is required (check with your glass box manufacturer) for warranty etc
I’d be inclined to add a piece of solid wood to the top ... but could also be convinced otherwise