TLDR: No, it is not more than 100 % efficient, the test performed was probably invalidated by using a heat meter assuming water as a heat transfer fluid, while propylene glycol/water mixture was actually used.
Some details about how test was performed can be found on a Czech reseller site:
- Ion boiler STAFOR 3-5
- Circulation pump Vilo 25/7
- Radiator Korad T22 300/400 500w
- Ion boiler control panel STAFOR 3-5
- Heat meter Dunfos Sonometer 1100
- Electricity analyzer Fluke 430
- Thermostatic sensor
- Hydraulic protection group
- Performance checking stand made from copper pipes
Details about how those pieces were connected are not described, but most likely it was more or less what can be seen in the YouTube video at 0:07.
When checking for individual pieces of equipment used, one thing looks very suspicious, and that is Danfoss Sonometer 1100 is intended to be used with water as a circulation medium. In this test a different liquid was almost certainly used, as the liquid required by the boiler to operate is heat carrier STATERM EKO E40, which is "made on the basis of propylene". By "propylene" the propylene glycol is most likely meant here (melting point -59°C), which is commonly used as a Heat-Transfer Fluid (it could hardly be a propene, which is highly flammable gas with boiling point of -47.6°C.).
As the ultrasonic heat meters compute the energy by measuring flow and temperature and multiplying measured volume with specific heat capacity, by assuming water properties on Propylene Glycol water solution an error is made.
Propylene Glycol based Heat-Transfer Fluid with boiling point 120°C is approx. 85 % Propylene Glycol (see Boiling Point of Aqueous Propylene Glycol Solutions), with specific heat capacity 2.51*0.85+4.18*(1-0.85) J/(gK) = 2.76 J/(gK) (see propylene glycol specific heat capacity and water specific heat capacity), which is 1.51 x lower than water heat capacity, therefore apparent heat transfer is approx. 1.51 x higher than it really is. Given Propylene Glycol concentration is not given, I only estimate it, I found the result close enough to be likely explanation of the 1,57 COP result.