I think virtually all of Stern's cabinets have been made by them / a third party contractor since the autumn of 2015, and small numbers before that. CGC (Churchill) were displaced from cabinet making some time before playfields.
The cabinets have been getting progressively cheaper for a while. I haven't seen a BM'66 or Aerosmith in the flesh, but would doubt they've improved. However, from my MoP and Luci to the new style SAM backbox and cheaper, lighter cabinet in my ST, there is a big difference. Bigger difference still between later Spike system games (non-CGC cabs). The GoTs and GBs that I've seen and played have all felt very wobbly and cheap. Wood practically feels like balsa.
Amazing that they ditched interlocking joinery. How much does that save in cutting / assembly time per unit? 5 dollars tops, for something so important to the cabinet's durability.