Lane Check question

I posted a thread on the Sling Builders' FB group which has stirred some conversation. The original question was about why the Sling TSi POH says to do the Lane Check at 4000 RPM, whereas the Rotax 915iS OM says to do it at 2500 RPM. 

An answer on that would be great, but that lead to a side discussion with some people saying there's no point in doing a Lane Check anyway, as the ECUs automatically check everything and if there was a problem you'd already know as you would have a Lane light.

My contention is this: During the Lane Check, you're not just turning off one Lane to make sure the other one is working. It's true that, if either Lane was inop you'd already have a light. Instead, you're checking to see, when one Lane is turned off, how does the other Lane respond to that. For example, when you turn Lane A off, the RPMs actually increase as the remaining Lane B enrichens the mixture in response. This is why the Rotax manual says to look for RPM changes within 250 RPM. They also say to check fuel pressure within limits during the Lane checks.

I understand that the ECUs do some automated testing of the independent ignitions, but I don't think they ever automatically turn one Lane off in order to test the response of the remaining Lane, do they? My contention is, that's a reason why we need to do a Lane Check.

The other group claims even that test is done automatically. I can find no reference for that (still searching) and I would think, if the Lanes were turning themselves off and on automatically, we would see the RPM fluctuations.

Can anyone provide insight on this?

Thanks!