I just checked 3.6.9, Chief is right, it let you hold AB speed without AB. Glide, hold AB for few secs, release, you keed AB speed. Didn't know that at that time and yes, it seems strange for me as well, here I need to agree with Goober. Let's keep newtonian physics out of here cause we all know we'd be accelerating infintely (as we got inifite fuel :-)).
For me the most logical behaviour would be adding speed vectors when changing direction during glide and applying throttle/AB, but let you achieve AB speed only with AB turned on, otherwise normal ship speed would be maximum. It contradicts newtonian all the way, but whole SCP does that anyway. Leaving it as it is/was (maybe but WCS but you can always make a flag) for me is little bit cheaty. I've caught myself exploiting that in TBP to fly significantly faster to some target in straight line, it's exactly like infinite AB fuel.
As to the second issue, accelerating without throttle/AB with match speed, as we all agreed it's buggy maybe some fast fix for RC3? That would at least give back 3.6.9 behaviour. Eventual glide revamp could follow later (3.6.10+).