Good lord I'm imagining job applications and resumes in the Metroid universe... Because again, with my whole thing about different species being selected un/consciously for certain jobs and roles, that'll definitely be relevant. Like of course you have to bring up what species you are, even if it's not mandated in an application, everyone knows that if you choose not to disclose it, it's because you're not the species a certain job is looking for anyway. Being a certain species IS part of your resume, and those fill-in features they use for particular skills applies here; So if you select one species, all of the traits associated with you are automatically listed.
For another example; Species with good peripheral vision, who can stay awake for longer periods of time... Anyone with an acute awareness of their environment; These would be hired as guards, be it in prisons or as generic security. Night vision is often a must. These species don't really need to be adaptable the way Earthians are because they're usually operating in an artificial, standardized environment, i.e. their workplace.
Plus, the architecture; Accommodating a wide variety of species' body types and needs can be difficult. With how species can vary in size wildly, you usually play it safe by having big, open spaces, with big, open doors and hallways and the like; Decreases the chance of some poor species being unable to fit through, getting caught in the doorframe, etc. Revolving doors are probably out of the question. Not to mention lots of canals to accommodate water-breathing species who visit.
This is especially the case for Daiban, which is the capital of the Federation; It needs to represent the Federation, which is supposed to represent all of the species involved. It reflects badly if Daiban's architecture isn't accommodating, especially for worlds that are 50/50 about joining the Federation, and whose ambassadors are visiting its capital for the first time to discuss things. Visitors to Daiban might feel eclipsed by the architecture, because it's so spacious and the buildings themselves larger to contain all that additional interior space; But for some species, Daiban is just the right size, and Federation representatives sigh in relief over that.
And what becomes the norm for the Federation, eventually starts bleeding in to other worlds, some of which are far from the capital because immigration will always be a thing, it's why the Federation even exists to begin with. But of course, to have more space, you need bigger walls and the like, which means more building materials; That can get more expensive, so the desire to accommodate different sizes might strain against companies and governments who want to be cost-effective, it's a balance of priorities. So some might try to get around this by emphasizing outdoor meetings, or prioritizing which buildings need to be 'accommodating', with immigration offices being the most obvious example.
Are there architects who specialized specifically in 'standardized' architecture designed for these purposes? Do different foods have different labels and signs of approval by certain organizations, such as a stamp asserting X product is vegan, kosher, halal, etc.? Specifically; X product is safe for a certain species. And again a lot of it can be expensive so it's cheaper sometimes to just stick with your own world where everything, specifically the infrastructure and logistics, is already tailored to you.
But the species with the most recurring traits, the 'bell curve' as we call it? They're the most populous, they're the ones who get the special treatment because they're seen as more viable, more profitable. The bell curve species are the ones best suited to thriving in different worlds. Jack of all trades, master of none, but better than master of one; It depends on what an employer might be looking for. So we have Earthians and other species amongst the 'bell curve', and its existence could have a scientific explanation, or just be sheer coincidence.
