If this sentence does not break across the bottom of the first and top of the second page then the results of this test are invalid; the UA is using some additional page-breaking restrictions or cannot parse page-break-inside: auto. (Also, exactly two lines of text should have fit on the first page.)
If page-break-inside: avoid is implemented, this sentence will start at the top of the fourth page.
If page-break-inside: avoid inherits or affects descendants, then this sentence will start at the top of the sixth page.
If page-break-inside: avoid does not affect descendants other than through inheritance then this sentence would have started at the bottom of page 7.