My best guess: probably to make sure that there's no confusion between words for "blow," "puff"
[φυσιάω, Ep. part. φῡσιόων:—intr.,
A. blow, puff, snort, breathe hard, pant, ἵπποι φυσιόωντες Il. 4.227, 16.506; μόχθοις ἀνδροκμῆσι φυσιᾷ σπλάγχνον A. Eu. 248; φυσιῶν . . ἐκβάλλει ῥοὴν . . φοινίου σταλάγματος S. Ant. 1238: metaph., μέσφʼ ὁ δαίμων οὔρια φυσιάει Cerc. 4.49.]
and words involving "becoming," "nature," etc., e.g.
[φυσιόω, (φύσις)
A. dispose one naturally, c. inf., Simp. in Epict. p.58 D.:—Pass., πεφυσιωμένος, η, ον, having become a second nature, inveterate, Arist. Cat. 9a2.]
Perhaps Dr. Moshe will shed more light on this issue.
P.S. Have you downloaded your LSJ yet? Very useful!