There is nothing that Adobe can do about this algorithmic quirk on the part of Microsoft.
A font such as Adobe Caslon Pro has a number of tall “ornament” glyphs and I suspect that Word is using their height for determining what Single spacing should be. Instead of taking the text point size and multiplying it by some factor (often 1.2 such that 10pt type is set with 12pt leading and 12pt type is set with 14pt leading), Word seems to look inside the font for some metric such as the height of the tallest glyph in the font. The base cause of this anomaly is that Word has its own heuristics as to what Single spacing (or for that matter, Double, or Triple spacing) is. When I get back to my office in mid-February, I will see whether with Word 2016, the spacing differs on screen than for PDF output or printing.
Using Word 2013 with Adobe Caslon Pro with paragraph line spacing set to Single, I see the same extra spacing on screen as for PDF output or printing.
