What’s interesting about living downmarket is PMF is critical. By definition, you’re building something for a high volume of customers, so the problems you’re solving need to be universal (or at least regularly recurring). One-off problems / solutions are not a recipe for repeatability.
So when B2B product companies start on the low-end (think SMB or Commercial space), they are forced to identify the most critical and concentrated use cases. To contrast that with going upmarket, your mindset shifts to solving peripheral problems that are more custom, because you’re incentivized to pack more into your existing distribution channel vs finding new channels (i.e. easier to renew / expand existing customers vs landing net new accounts).