I did a test in a simpler market, ATL-TPA on Delta, on Expedia.com
Leaving June 27 and returning June 30 returns a one way K fare of $179 that requires a 3 day advance purchase and a one way T fare of $72 that requires a 7 day advance purchase.
This makes sense, because requiring the same advance purchase both ways on one way fares is pointless, as one could simply buy two one way tickets. Possibly "most restrictive terms apply" only applies to roundtrip fares since booking separately is not possible.