Replace oil heating in a 60s house?

The annual performance factor then certainly lingers around a 3.

Which would be completely fine for a poorly insulated house with radiators, don’t you think? If that bothers you, you can insulate.

But let's be honest... a partially renovated house from the 60s will hardly come in below 200 kWh/sqm, there are also plenty that are rather around 300 kWh/sqm. Let's calculate 150 sqm * 200 kWh/sqm, then we have 30,000 kWh heating demand. Let's assume 55 degrees flow temperature and 2 degrees outside temperature (that's already a mild area) and ignore that the performance on cold days drops much more than it compensates on warmer days. Then we come to a COP=2.12, which makes 14,150 kWh electricity for heating or 5000€ upwards. This is still rather optimistic, the house partially renovated, mild winters, not an oversized house, electricity at 35c. Reality can look significantly worse. I don't need to look at any more favorable expert reports when I can calculate it myself and come to the conclusion that it's nonsense. Such houses are simply not economically convertible without comprehensive renovation. Period, end.

a partially renovated house from the 60s will hardly come under 200 kWh/sqm,

So we don’t need to discuss anything over 200 kWh/sqm, in my opinion. The house was negligently neglected, NOT partially renovated, and needs to be revised as soon as possible.
And then the big mistake in your calculation lies in the assumption that you need 55° at 2° outside temperature. The supply temperature is always given at the design outside temperature (NAT) (somewhere between -9 and -12°). So the 55° are statistically only needed 24 hours a year. Average winter temperatures in the lowlands are around 7° and there roughly (estimated) 30° supply temperature is enough. And then the difference to the heat pump designed for 35° supply temperature (at NAT) is only about 6°, and on average over the year that makes only a difference of 14%.
Oh, what am I talking about – you can read, I have provided you with search engine hints. Refute the study with your own measurements or calculations, THEN we can continue to discuss.

The table does not say NAT, it says "Outdoor Air" meaning outside temperature. And the oil heating system is certainly designed for 55 degrees or higher, a high flow temperature doesn't cost anything there. For 7 degrees average temperature in winter I would like an example, even well-known mild winter places like Konstanz are significantly below that for 3 months

For an average temperature of 7 degrees in winter, I would like an example,

You are right, I expressed myself incorrectly: It is the average temperature during the heating period, not during the meteorological winter.

During the heating season, the temperature in my area of central Lower Saxony is often between 0 and 4 degrees AT. I have a thermal balancing, large radiators, and have lowered the supply temperature as much as possible. At +7 degrees AT, I do NOT reach 30 degrees supply temperature. More like 38. And this with 24 cm wool on the upper floor, insulated windows, and some facade insulation. At some point, lowering the supply temperature and radiators simply reaches its limit, as they massively lose heating performance.