I'm not sure he's entirely correct in saying the following:
Reading adjacent blocks of data is no faster than reading blocks that are spread out over the drive. Fragmentation does not affect SSD drive speed.
If you look at benchmarks, all
the SSDs have different speed characteristics when dealing with linear reads/writes compared to scattered smaller I/O. It can matter a lot for writes, but also matters for reads.
I agree fully that defragmenting SSDs is a bad idea, because of the limited amount of erase-cycles of the flash cells. It might
make sense to defragment individual files if they're heavily fragmented; you'd do that by moving the file to another drive (on a mechanical disk, prefarably), then moving it back to the SSD (using a tool that tries to allocate the entire chunk contiguously).
Also, I see a guy in the comments recommending a single defrag after you installed all your apps. Don't do that - if you want the SSD defragged, start by installing to a mechanical disk, defrag that, and move the install to the SSD using, for instance, Paragon Virtualization Manager
Similarly, if your SSD ends up heavily fragmented, create a disk image of it to a mechanical drive, defrag that image, do a single-pass wipe of the SSD (to let the drive know all
blocks are blank, useful for the reallocation algorithms), then transfer the defragged image back.