They're correct: ARM won the mobile space, won Apple, and is very gradually seeping into wider availability for other operating systems.
Never mind the majority of raw FLOPS these days are almost certainly going through GPU architectures.
The first generation of true 16-bit CPUs, i.e. Intel 8086, Motorola MC68000 and Zilog Z8000, had almost an order of magnitude more transistors, i.e. in the range of 15000 transistors to 50000 transistors.
The first true 32-bit CPUs, like the National 32000 series, Motorola MC68020 and Intel 80386, had a few hundred thousand transistors.
By the end of the eighties, the second generation of 32-bit CPUs reached 1 million transistors.
The model number was decided long before the transistor-level design was finalized.
The 68000 transistors number claimed by the Motorola marketing was close to what you get by dividing the die area to the area of one transistor, so it did not correspond to actual transistor positions.
The MC68000 die had large areas occupied with microprogram ROMs, and there as you say only a part of the array of transistors are active, depending on the stored bits. Nonetheless, a significant part of the die was occupied with random logic, where all the physical transistors are used and a part of the area does not have any transistors.