LUCENE-2605 introduced the classic query parser option to not split on whitespace prior to performing analysis.
From the javadocs for QueryParser.setAutoGeneratePhraseQueries():
phrase queries will be automatically generated when the analyzer returns more than one term from whitespace delimited text.
When splitOnWhitespace=false, the output from analysis can now come from multiple whitespace-separated tokens, which breaks code assumptions when autoGeneratePhraseQueries=true: for this combination of options, it's not appropriate to auto-quote multiple non-overlapping tokens produced by analysis. E.g. simple whitespace tokenization over the query "some words" will produce the token sequence ("some", "words"), and even when autoGeneratePhraseQueries=true, we should not be creating a phrase query here.