Since there's no dipstick for trans fluid, am I to NEVER flush the transmission, at any mileage?

Change transmission fluid at 50k, 100k and 150k

nspect fuel system for damage or leaks. • ••••• Inspect exhaust system for loose or damaged components. • ••••• Replace engine air cleaner filter. See Engine Air Cleaner/Filter on page 330 . ••• 2.4L (Code B) L4 and 3.5L (Code N) V6 Engines Only: Change automatic transaxle fluid and filter (severe service only). See footnote (h). ••• 3.9L (Code 1) V6 Engine Only: Change automatic transaxle fluid and filter (severe service). See footnote (h). ••• 3.9L (Code 1) V6 Engine Only: Change automatic transaxle fluid and filter (normal service). • 3.6L (Code 7) V6 Engine Only: Change automatic transaxle fluid (severe service). Page 434 from link↓

http://www.vadengmpp.com/owners-manual/pontiac/2007-Pontiac-G6.pdf

Notice it says change, NOT Flush