That's basically it. The 286 has a much larger wafer inside than a typical DIP, and DIPs are extremely inefficient packages.

It would be interesting to see how much you could shrink this board down if all these chips were replaced with BGAs (using the same wafers inside). Obviously, that's not really feasible (no one is selling a BGA version of an 8259 interrupt controller, much less an 80286), but it would be interesting to see the dramatic size reduction, just from packaging waste. Also interesting would be if you designed a board using BGA versions of all these chips, but fabbed on modern IC processes (thus yielding much smaller wafers. and therefore somewhat smaller BGA packages). Of course, the whole thing could probably just be implemented with a single FPGA these days.

They are obviously ICs, but being programmable they’re general purpose, not application specific (the AS in ASIC).