No, but that raises a good question. It has been reported that the ecu will retain "I have an 02 sensor config" until the power is disconnected. Upon power disconnect-restart ecu supposedly checks just once for an O2 or CO pot and also checks to see if a CCP is installed and what jumper setting. The re-set instructions were mainly for pp switching over to CO pot from lambda but are normally followed for other mods and any sensor changes.
That you are willing to take the time to do this test and report your result will be appreciated by other 1100 owners. If you want to simulate what the shop says occurred, then no, do not re-set the ecu power after disconnecting lambda. The ecu should generate a "bad 02" fault code. Maybe ask your tech which lambda fault code he read? Shorted to ground?, Open? ect. We do not know at this point what type of lambda fault the dealer detected. The ecu is capable of storing several diiferent types of lambda fault codes. My understanding is that regardless of the kind of lambda fault detected by the ecu, its response should be the same which is to ignore the sensor.
If you disconnect then you will be simulating the open circuit fault. Idling should be affected to some extent, followed by the ecu slowly adapting to running w/o lambda. That isn't the issue. You just want to see if the top speed limit returns. Not many expect this to happen but who knows? Perhaps ride a few days w/o lambda so the ecu can optimize its "dead lambda" compensation settings. Once you finish making observations w/o lambda and it is reconnected, then definitely re-set the ecu to clear fault codes so that the ecu can again recognize that a good lambda is present. Just as before, you will have to ride for a few days under varying load conditions for the ecu to optimize.