There is no doubt that using either heating or AC in EV's does make a noticeable difference to the available range of the car. Whether is fair to describe it as a "major issue" will depend on your point of view, however using AC is as much of an issue in ICE vehicles if you look at how it affects MPG. It's not noticed as much becasue ICE vehicles presently do have a better overall range, so its less obvious how using AC does affect the car. But as its energy usage and that energy is sourced from the fuel used there is a cost for both ICE and EV owners.
There is no doubt that needing to heat or cool and EV's cabin does use battery resources, but I, and other web based sites were practical experience has garnered evidence disagree with the 50-60% percentage losses suggested in the paper OC points to.
We need to consider heating and cooling separately.
Heating the cabin needs a source of heat. Conveniently becasue ICE engines throw away 60 to 80% of the energy in the fuel as waste heat there's plenty to grab. Unfortunately becasue EV's one lose about 10% of the battery energy, and it's not always easy to harvest it many EV's need to use direct heating elements run from the battery. As we know present day EV's have a more limited range the ICE, so any additional drain on the battery can make an appreciable difference.
However an increasing number of EV's are using air heat recovery systems, which effectively uses an Air Conditioning system working in reverse, where the system drags heat out of the exterior ambient air and pumps it into the car. Using such systems its entirely possible to use 1kWh electrical energy to scavenge 2to 3kWh of heat from the outside and this can make quite a difference and reduces the loss of range - still not as good as ICE heater, from the cars performance. but streets better than burning fossile fuels in and ICE to produce waste heat.
The story is differnt for Air Conditioning (AC) to cool the cabin, and in fact the roles are slightly reversed. AC uses mechanical energy either from an electric motor to drive the AC's compressor or as a belt driven take off from the ICE. Either way for an ICE vehicle that mechanical energy is derived from the IC engine, and that means it is just as wasteful of fuel. If the ICE uses an electric motor driven compressor, then you have the additional losses associated with the cars alternator etc. The engine power used by the AC can be felt when its turned on, and the engine reacts to the load. This load needs to be fuelled so either you accept lowered performance from your vehicle or use more throttle thus more fuel. This hits MPG and of course costs more. The effect is even more noticeable in smaller engined cars.
In addition, as the IC engine and exhaust is close to the cabin in most cars, the fact they are hot it will add heat to the cabin which the AC is asked to remove, so its very likely AC in an ICE will have to work harder or longer than in the equivalent EV.
In the EV, the AC will have a dedicated motor which is inherently more efficient than the ICE system. Because EV's produce so little excess heat, the cabins are inherently cooler, so the AC has less work to do thus saving battery usage.