Many (better) models are fitted with heat pump devices. All batteries produce heat when either charging or discharging, so some heat is available, soon after starting on a journey. At other times I would guess the heat pump might take heat fro the air? Add to that a heated steering wheel and seat options, will provide quite a lot of personal comfort for the driver at much reduced power draw.
On top of that, halving the range with just cabin heating is a ridiculous claim, unless the battery is already a small one (so a ‘city’ car rather than a long distance model.
Most certainly the range is reduced during cold weather, but also for ICE cars as well (although not to such an extent).
Personally, I don’t see the initial claim to be relevant for (most) current models.
Too many ‘negative’ postings turn up re BEVs. They are improving all the time – and becoming cheaper.