Warframe – What Causes Change of Mission Type During a Play-Through? Explained

If the timer runs out before you get to extraction, you only lose the credit reward. All mods, resources, mission reward mods and items will be kept. The next mission is also unlocked.

(As of Update 9)

Forgive me if I'm off topic of your question but this is how I can think to answer your oddly phrased question.

According to the wiki:

Killing an enemy with a warframe ability (molecular prime) will grant 100% of the experience from each enemy killed to your warframe. If you use weapons, it splits the experience 50/50 between your warframe and weapon.

When you're playing co-op and an ally kills an enemy, the experience gained is equally divided between your frame and each weapon.

According to personal experience:

When I first started playing warframe I had my friend explain the experience mechanics to me. He was probably completely wrong but it actually does make sense. He's told me that when you kill an enemy with an ability/weapon, you get 100% of the total experience toward your correlating weapon/frame, and then it divides the experience between your other gear. This CAN NOT be 100% correct (since I've never actually levelled a secondary by using my primaries) but I don't think hes too far off of the actual answer.

In all this leads me to believe that, when you kill an enemy with an ability, it gives you 100% of that total experience to your frame and then an additional bonus to your weapons. In regards to your "leeching method", its an inaccurate test according to this:
Kills: You get a bonus 50% experience from all kills at the end of mission.
If you want an accurate comparison, multiply your experience from the kill run by 2/3 (100% + 50% = 150% total, 2/3 of this would be 100%).