That might be it. It would be a convenient and efficient way of
adjusting brightness. They also might be compensating for voltage and
temperature by changing the pulse width.

Hi Roy, You can do all the above with a regular light bulb. I think the
reason they use multiple LED's is to reduce the mean time between failures. If
a regular bulb fails, you are dark. If half of the LED's fail you still have
light. They generally have 20 plus LED's. in the stuff I have seen. Also,
LED's tend to last than bulbs (I think)
73 Gary N4AST