http://dictionary.reference.com/browse/benchmark
bench·mark
1. a standard of excellence, achievement, etc., against which similar things must be measured or judged: The new hotel is a benchmark in opulence and comfort.
2. any standard or reference by which others can be measured or judged: The current price for crude oil may become the benchmark.
3. Computers. an established point of reference against which computers or programs can be measured in tests comparing their performance, reliability, etc.
–adjective
4. of, pertaining to, or resulting in a benchmark: benchmark test, benchmark study.
http://dictionary.reference.com/browse/milestone
mile·stone
1. A stone marker set up on a roadside to indicate the distance in miles from a given point.
2. An important event, as in a person's career, the history of a nation, or the advancement of knowledge in a field; a turning point.Benchmarks are reference points from which to evaluate other things of similar nature. Milestones are measures of progress against some plan.
Benchmarks are specific markers set by the US Geological survey establishing precise elevations around the country; surveyors use them as the starting point from which to determine topology.
Milestones, originally markers along a road, are a commonly used term in project management. Achieving a specific milestone is a measurable goal in a project plan. You don't "achieve" benchmarks. The metaphor is just wrong. "Achieving" a benchmark would be going and standing on the USGS marker which is already in place. Doing nothing. Achieving a milestone would be going someplace, doing something. Something which is a prerequisite to doing something else.
This "gang that couldn't shoot straight" can't even pick the right slogans to spin their bs.