[RPG] Are spectators born the same way as beholders

While the general section on beholders in Lords of Madness doesn't give any particulars of the furniture in the beholder's lair, there is an example lair detailed later in the chapter (page 56). I won't reproduce the whole thing here, but the important room for our purposes is the beholder's personal chamber:

This large chamber is quite impressive; the walls and ceiling are covered with intricate carvings depicting beholders eating humanoids, and vast fields of mushrooms with writhing tendrils. On the ceiling above, the image of a single immense beholder watches everything. Two large, uneven stalagmites protrude from the floor along the northeastern wall, and to the south stand several well-made statues of powerful-looking adventurers and fearsome monsters. In the center of the room sit numerous desks, each of which is covered with mounds of papers and books.

This chamber is Sekarvu’s personal lair, and where it spends the majority of its time.

There is no mention of a bed, or indeed any furniture beyond the desks. So either the beholder sleeps on a desk (face it, we all have occasionally), or it continues to levitate while it sleeps.

A possible source of further details on beholders would be the AD&D 2e book I, Tyrant, which was the book in the Monstrous Arcana series dedicated purely to beholders.

I think the intent is clear from how the two work together. The froghemoth takes half damage from lightning, but on that turn the froghemoth has a hit to its AC and speed. My guess at the author's intent is that doing all that other stuff and taking the full amount of damage would have made the monster too weak, so halving damage allowed them to add the interesting effects.

Moreover, in previous editions (3.5 at the very least), the froghemoth was immune to lightning damage, but would instead take a speed hit. As far as 5e goes, I don't recall any other creatures that have both a similar resistance plus other negative effects from the same damage type.