All you have to do is boot from a TRIM enabled SSD running OS 10.10.4. Otherwise, you are correct on running Repair Disk—and you must in 10.10.3 and earlier. This is backwards compatible to 10.6.8. In El Cap, the reports aren't very good.If you want to trim your boot SSD, start up from an alternate boot drive with Trim enabled and run Repair Disk in Disk Utility
This is the same family that Apple is using in newer Mac Books so yes, I bought a couple for my wife and daughter and service a few more. I don't know why you think this should matter.Mike - Do you own any SM951s?
Apple disabled write to zeros in 10.11.x for SSDs and crippled it for HHDs. I'm with Apple on solid state and disagree re HHDs. I know what test to run to see if I understand why on HHDs—if I am curious enough and make the time.
As of June, Apple no longer offers a MacBook with an HHD unless you find any in the Refurb Store (none today). It's no secret that the Minis and iMacs will follow suit as solid state drives come down in price.