LED signal light issues.

What I don't understand is where people got the idea that 4 of #1157 bulbs are a massive electrical load under the dash.

Well 4 1157's are not but those along with all the dash lights, headlights, tail lights, wipers, heater, stereo and whatever else is.
That's part of why at idle headlights dim, wipers slow, signals slow, and heater blower slows and CCR plays Born on the Bayou in a different key.
Well, just kidding about that last part. :D
After swapping markers, signals, tail, brake, interior and cluster all over to LED that doesn't happen any more.
Plus you can accidentally leave your park lights or emergency flashers on for 3 days without killing the battery. :D