They were likely actually referring to MLC vs TLC vs QLC. All three types can be manufactured in the stacked "3D" form.
MLC stores 2 bits per cell, TLC store 3, and QLC stores 4. MLC is the fastest and most reliable form, while QLC is the cheapest.
The MacBook Pro likely uses TLC like the vast majority of current consumer machines. Apple's SSDs are typically among the fastest available, but I haven't been able to find anything about reliability.
Nobody is manufacturing planar NAND flash memory in high volume or in die sizes large enough to fit multiple TBs of flash into a notebook. The only viable options currently being manufactured are all 3D NAND. The vast majority of this (and what is used by almost all SSDs across all market segments) is 3D TLC NAND flash memory—TLC meaning it stores 3 bits per physical memory cell. MLC would typically refer to storing two bits per cell, SLC means one bit per cell, and QLC means four bits per cell.
There is no reason to prefer MLC these days. TLC has plenty of write endurance for client/consumer usage. MLC offers theoretical advantages in performance and endurance, but these are absolutely not worth the higher cost that comes from lower density. (And that's comparing 3D MLC against 3D TLC; high-density planar MLC loses against 3D TLC on all counts.) There is a niche market for SLC NAND in high-performance server applications that need the lowest possible latency from their SSDs, and Samsung and Toshiba are currently manufacturing memory to suit this use case. But it again has density too low for multi-TB SSDs to fit into a laptop.
