Well, yes, but you can heat the ventilation air with a gas boiler or heat pump. But they both have a greater cost and greater maintenance bills than a simple electric heater.
Indeed - if you're heating with ventilation air then an electric heater is the logical way of doing it. Where I disagree with them is the assumption that heating with ventilation air is particularly desirable - it works for a particular occupant density, climate and insulation level, but I'm not convinced that designing a standard around it is particularly desirable. All it really saves is a few radiators in some (not all) rooms - which seems to be a fairly modest benefit to me.
I think a heat pump with an SPF of 5 is still fairly unusual, but perhaps I'm out of date.
Unusual but not unknown - and more importantly it's easier to do the sums with 5:1 than 4.6:1

There are problems with basing a standard on primary energy given that it gets used for DHW production and many other things besides space heating and that there are many different ways of measuring primary energy depending on what fuel it is, how that fuel is used, whether it's supplied externally or from the site (e.g. solar, wind or hydro). In fact I was lucky that PHI have updated their PE calculation to a PER calculation, since previously it had been almost impossible to certify a passivhaus with an entirely resistive electric heating scheme. So I would have been forced to buy a heat pump, perhaps a 'combined unit'.
Thing is, they've had a primary energy standard of some sort all along - the use of PER has made it rather more rigorous, but it isn't a new idea. When you look at the impact of a house on the environment, it's primary energy that has an impact. I wouldn't get rid of a heat demand calculation at all - doing it and setting a standard is going to be required for comfort reasons - but the 15 kWh/m
2/year or 10W/m
2 standard don't make sense as the correct place to put a stake in the ground for me: I'd sooner see a slightly higher W/m
2 standard, set by evidence of comfort levels, and keep the PER limits and maybe emphasise them a bit more.
DHW production is a pretty important point though - PH is at the stage where DHW is a bigger energy user than space heating, but the emphasis is still on the space heating target: since DHW use is limited to a few appliances and there are established ways to economise on it's use, this makes little sense to me. It comes out in the wash of the PER calculation at the moment, but I'd sooner see it emphasised a bit more since it and plug loads are the main consumers.