That's essentially the lava flow anti-pattern. You have remnants of old architect/tools/philosophy left in the old code while the new code is being built with

That's essentially the lava flow anti-pattern. You have remnants of old architect/tools/philosophy left in the old code while the new code is being built with the new hotness. Invariably everyone has to learn the old stuff to maintain the system as well as learn the new stuff to keep building.