Noise and intermediate ISO settings

Just read this which I'd not seen before:-
"Here is one ISO tip that many photographers aren’t aware of: keep your ISO setting to the industry standard numbers – 100, 200, 400, 800, 1600, 3200, etc. All digital cameras offer ISO settings between these numbers (such as ISO 250). But, what is really happening (with many camera models) is that the camera has electronically boosted the sensitivity of the sensor to ISO 400, then cut it back to ISO 250 using an algorithm, and this will increase the noise beyond what you might expect for that particular ISO setting."
1. Is this true and if so what is the point of intermediate ISO's?
2. Does it apply to Pentax DSLR's?
3. What does it really mean in real terms of IQ ?

Source please? If it came from a Pentax engineer it's probably right, if it came from somewhere else, who knows! I find that hard to believe though.

What would be the logic behind boosting the signal above what's needed and bringing it down after instead of just boosting it to where it's needed:::

I've posted this many times before on here, but people just
don't seem to read Goes back to the K10D days at least.

If you know YOUR camera you shouldn't need to be told

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Just because someone says something on an internet forum doesn't necessarily mean its right, does it?!

Here's a link to an article about it. link

I got bored before finishing it......the general gist seems to be that an intermediate setting gives the same amount of noise as the next full stop, ie ISO 160 has the same noise as ISO 200.

Wow, that is heavy going!

Rice High made mention several years ago: http://ricehigh.blogspot.com/2011/04/should-you-use-intermediate-iso-speeds.html

It seems it all depends how the firmware is programmed.

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http://www.lightstalking.com/digital-image-noise

Item 2. under - Tips to combat noise generation.

I was puzzled by it and wondered if it had any credence. Not any clearer so far!