From 2011-2014 Riverheads played in 2A
2011: 12-1 - Season ended with 28-14 loss to State Champion Gretna (Gretna's next two games had very similar margins of victory)
2012: 10-2 - Season ended with 22-21 loss to Wilson Memorial, who lost to State Champion Goochland (Went for 2 and lost) Also note RHS beat Goochland, led by the same players, in 2013
2013: 12-2 - Season ended with 28-7 loss to State Champion Giles (Some would mention starting QB was out with injury, but I don't consider that an excuse, just a story-line)
2014: 11-1 - Season ended with 28-27 loss to King William (Missed XP got em)
6 losses in 4 years is good for any program. 7 playoff wins in 4 years is good for any program. Playing into the second round or further, including a State Semi, each year is good for any program.
I believe those results show that Riverheads competed in those 4 years. Did they win it all, no, but there have 3-4 year stretches between most of their state titles dating back to 2000. Only this recent success has resulted in consecutive trips to the State Title Game.
Since dropping back down to Class 1, where they where for all years prior to 2011, Riverheads is 24-5 vs Class 2 competition.
It is my opinion the Riverheads would compete at the 2A level as is. Are they the only school I would make that statement for, no. By saying that, I believe they are capable of beating top level 2A teams. How they match up with specific teams from specific years is up for debate and there is no way of knowing, but with the facts we have in front of us, I think it is obvious they would compete.
All of this said, I think most top level teams at each classification could compete at the classification one above them. I don't believe this is a Riverheads thing. Appomattox could have competed in recent years with the top of Class 3. I believe Blacksburg and Magna Vista could compete at Class 4. I believe Salem could compete with Class 5. I believe Highland Springs and LC Bird can compete with Class 6 teams.
Inversely, Phoebus was running through division 5 from 2001 to 2011. 2018 is the first time the Phantoms have earned a spot in the State Title game for Class 4 or 3, where they have been since. In 2011 they won the state Title game vs a school with 700 more students then Phoebus had.
It just doesn't come down to that class number 1-6 to determine how good you are. You can be a class under and still compete, you can have success at a higher class and that doesn't ensure success as classifications lower.
In the end, I do partially agree with you. If Riverheads again wins the State Title in dominate fashion, it shows they have separated from a large majority of Class 1. Where I disagree with your inference, is they should not be forced to move to class 2 because of their recent win/loss record. The VHSL has done right by all teams in the state by creating a system that is based on enrollment numbers and those classifications are built by a nearly equal amount of teams. Now, if the line moves and that puts Riverheads in Class 2, I would have zero problem with that. But since they just went through planning for the next cycle, and that didn't happen, it is irrelevant for the next 4 years.
You know who was terrible in football prior to 1997, or so? Riverheads. They got better, developed a program, stayed consistent, allowed their players to be multi-sport athletes, didn't burn players out with year round practice, and let winning breed winning. It has worked for them. Maybe other teams could try making themselves better rather than moaning one team is winning too much.