Their 3-bet-or-fold defense means a polarized-but-real range; continue with position and a plan.
The reference tier. 4-bet a tight value range, call with hands that flop well, fold the rest without ceremony.
The small blind 3-bets your cutoff open — a range built to play fast, because playing slow out of position deep is misery.
Assumes a standard 3-bet; 4-bet to ~2.2–2.5x the 3-bet. Deep, favor calls over 4-bets — a 4-bet pot at 500bb+ commits you with range disadvantage.