High and Fast vs Low and slow, which reduced SAM, AAM range better?

I used to think the higher you fly, the shorter the enemy missiles range is, however according to these 2 graph, it seem that flying high decrease enemy’s SAM range but increase their AAM ( if launched from altitude around 13- 15 km) , any explanation to that?

Second question, which will decrease SAM range better? flying at 60 k feet at mach 1.8 or flying at mach 0.5, sea level ( assume radar horizon isnot a problem due to AWACS, and very big SAM like SM-6 or 40ND)