It's called stack ranking, famously from Jack Welch at GE. Also famously bad, bad, bad practice. Well it can be effective in the case a company has never had a layoff, nor fired anyone. There will of course be low performers in the org. Stack ranking can work in this case to cut them out. After a few interations you start letting go the perfectly competent people. The this all then plays out is teams hire people to fire, employees become super political and self serving, moral goes into the ditch.
DST, already having negative moral, and a layoff that's thinned out the worst performers (right? right?), will most likely move into the "hire people to fire them" if this is in fact what SS&C is mandating.
Incomptents just copy and ape the successful without understanding or nuance for their situation. Stack ranking is a terrible, ineffective practice. True to form SS&C and DST just muddle along, they really don't have any idea what they're doing. Hence their employees don't either.