I also had come across such situation while doing "Edit Entire road" and A-B markers were shown in the middle of the highlight road. Here's link to that road:
http://www.google.com/mapmaker?hl=en&fll=26.671314,87.703171&fr=0.001534,0.001717&mpp=4.268990&gw=12&ll=26.690871,87.701883&spn=0.05483,0.081711&z=14
To highlight it just now I've named that road to "#1 Road" just to check out how much of the road gets the new name - "#1 Road". As I had guessed "Edit Entire Road" applies the attribute values (road name change) only within the A-B bubbles range ! even though the highlight road is even longer than that.
What you do is, select any segment of the "#1 Road" and click "Edit Entire road" - The blue highlight marks 5km+ of the road, but A-B bubbles covers only about 3 km of the entire road.
However, if you select any part of the road above "#1 Road" and click "Edit Entire road" - no part of "#1 Road" gets highlighted though.
My assumption is, while doing "Edit Entire road", the range/length of A-B bubbles are restricted to 5 km length, and hence one of the A-B bubble markers being shown in the middle of the highlighted road. And in order to edit attributes beyond the range shown by A-B bubbles, one has to select a segment beyond the A-B bubbles on the portion of the highlight road and do "Edit Entire road" until you reach the actual end point of the road.
In the past, in this very map (some local roads in this map), I had seen A-B markers in 3 different places depending on which segment I pickup to click on "Edit Entire road". If I remember correctly, the total length of extended road was above 15 km. The author who drew the road liked "Extend road" option so much so - he drew entire road network that way. At that time, I asked the author to delete the road segments and limit "entire road length" within 5 km in length. But I let this portion of the road intact in-order to come back later and check how MapMaker would behave later as MapMaker evolve.
I guess this example explains a little bit of Gorio's situation.
Keshav