If you display:block a <span>, just take a <div> man.

I giggled 😅

- throws up the <div/> hand sign -

Also, please never add line breaks after your <span>s

I do inline-block, I'm chill.

Text needs to be auto-width for desktop, but 100% width for mobile.

Very common use case.

One could change their entire layout to one column with just

span {
display: block;
}

Inline-block would maybe still be better... but it would work.

@HiFiWiFiSciFi span is not meant for layout, span is meant for inline styling and semantics. Span shouldn't contain an entire paragraph, that would be <p>.
In the usecase you provided the right thing to do would be to enclose the span in a div, p tag or other block-level element and apply layout changes to that.