Going to the Villa game last month, I done my usual change at Cornbrook. There was a tram immediately in front and one right behind mine. There was then a queue of 4 trams behind that waiting as well. 4 doubles and 3 singles were operating in the same direction on approx. 300m of track. The electricity load reason is therefore total bullshit. As you correctly state, it's bad planning or they can't be arsed.Trams were proper rammed but it all went ok...............being crushed on a tram isn't pleasant.
The fact that no extra trams every few minutes are put on for these times is not great transport.
I've heard the reasons why (electricity load etc) It still stinks of bad planning.
The London underground seems to manage ok mostly.