When I quote "two words" in a group I expect to only get results based on those two words, spelled with those characters, exactly as quoted. Not split, not with different spelling or related meanings, not with anything but actually the string of bytes which I have quoted.
Google doesn't replace them with split versions (except that it ignores punctuation), nor does it replace them with different spellings or related meanings. The words you search for will be there, in order, the only difference will be all whitespace and punctuation is treated as a space.
>string of bytes which I have quoted
That's tricky. What if there's a line break? What if you search for "some text" but the html contains "some <b>text</b>"? Punctuation would be a problem too. What if you searched for something with "-" (hyphen-minus, unicode 0x2d), but the page contained a "‐" (hyphen, unicode 0x2010)? What if you searched for something with a dumb quote, but the page contained a smart quote? What if you searched for something with a space but the page contained a non-breaking space?
Or are you saying it returns pages without the text on it at all? I don't think that's the case.
Disclosure: I work at Google, but not Search.