I ran the numbers, and it turns out there's nothing to change.
Processing a fruit yields a seed at 2 %, but that recipe allows productivity, and the biochamber gives +50 % by default — so it's really 3 % per fruit. Vanilla: 50 fruit × 0.03 = 1.5 seeds per cycle. Ours: the seed comes back whole, plus 20 fruit × 0.03 = 1.6. The seed multiplication rate is the same, and the vanilla chain doesn't teeter on the edge either — it grows.
So switching to "50 fruit and consume the seed" would only change the yield per cycle — a multiplier, not a mechanic. It doesn't bring the pain spiral back: seeds pile up regardless.
Dropping the seed consumption was a deliberate call. Without a guaranteed return, the greenhouse stalls on a run of bad luck — and as the numbers show, there's nothing gained in exchange.
On quality you're right: the loop exists, but it's exactly the vanilla one — a legendary fruit yields a legendary seed through processing in vanilla too. What we've added is a price tag: crafting at a given quality requires ingredients of that same quality, and landfill is consumed at a fifth per cycle, so a legendary fruit stream runs into legendary stone from asteroids.