In Nepal, we refer to this new breed of trekkers lodges as comfort lodges. However, western tour operators (perhaps with overzealous marketing departments) promoted them as luxury trekking lodges (without seeing them for themselves), and as that seems to have caught on, then we do too.
These purpose-built establishments are (all things considered) a marvel, but let's not confuse them with a 5-star deluxe hotel.
Unlike the standard trekkers lodge or tea house, the luxury trekking lodges in Nepal tend to be part of a management group (e.g., ESL, Yeti Mountain Homes, Ker & Downey), and they are most certainly of a much, much higher standard than the basic trekkers lodge.
Of course they vary, but as a general rule, they all provide private, comfortable bedrooms with much more in the way of creature comforts than a simple tea house.
Cosy beds with clean linen, blankets/duvets are the norm as are the welcome addition of soft furnishings too. Bedrooms usually have electricity for lighting and usually some plug points. Sleeping bags are definitely not required.
Importantly all rooms are en-suite with western style flushing toilets, hot showers and hand basins. Towels are provided too.
The lodges will have a dining room, lounge area, and sometimes even a bar as well. Invariably, these luxury trekking lodges are in some fairly spectacular locations, and given their remoteness, you really do have to wonder how they were built at all. Many have some form of private garden, too.
Most, if not all, have free wifi.
The staff is usually professionally trained to provide a high level of customer service, and the meals served are of a higher standard than at a basic lodge. Unlike the basic tea houses, the meat dishes served at these luxury trekkers lodges tend to be safe to eat.
However, even these so-called luxury trekking lodges have limitations due to their locations, particularly heating. Most bedrooms will not have any heating source due to the limited power supply high in the Himalayas. But public areas will have a fire or stove, and at night your bed will either have an electric blanket or staff will provide you with a hot water bottle.
If you were to step inside a local's home in these parts of the Himalayas, then these comfort lodges are indeed luxurious in comparison.