The question came in 2 parts. Is it a go slow? No. Simple answer to that part. Then we have the ATC/Pilot interface problem/question. I am required to notify any speed changes from what is on my flight plan. I do so. I am required to wherever possible, fly the plan as given. Sure, I can fiddle around the edges, no problem. But changing from .63 at FL 260 to .78 at the same level or vice versa isn't really fiddling about the edges. Same as going from .79 to .71 FL 370. Also not really fiddling about the edges. Both examples would require notification to the relevant ATC, and MAY require answers to operations at the airline. The problem appears to be when a low level and consequently low speed plan is submitted. That may be for all kinds of factors, weather, wind, maintenance issues, volcanic ash clouds, whatever. The crew complies with said plan, and it appears that it raises issues with ATC who, at least on here, are claiming "we are not aware, " or, "you should tell us".
The point I'm trying to make is that the plan given to the crew is the same as the one sent to ATC, and that is what we will be doing. If there are to be variations from that submitted plan, then the crew are obligated to tell ATC of the changes. As it should be. Now, if the information in the plan is incorrect, not being read or unavailable, how, as a member of the crew, would I be aware of that from ATC'S point of view?