The post I responded to called Ed the perfect substitute and the best in the business. There were no positional qualifications in those statements.
And note, I didn't ask why hasn't Ed won the 6MOY award, I asked why he hasn't come within spitting distance of winning it. While it's true that the award generally goes to a high scoring bench player, each of the last three years, a player averaging less than 9 ppg has finished in the top 3 in 6MOY voting. Last year it was Fred Van Vleet coming in 3rd with an average of 8.6 ppg. And, in both 2015-16 and 2016-17, Andre Iguodala came in a very close 2nd in 6MOY voting while averaging 7.0 and 7.6 ppg. So, it is possible to at least be considered for the award based on more than just scoring.
Finally, if Ed is so valuable, why did he go to a bad team on a cheap contract? If he was so valuable, why didn't some contender snap him up for $4.5 million? Why'd he have to settle for going to BRK at $4.4 million?
I think you sort of answered that question yourself:
"the easy answer to this question is that what Ed does off the bench is not valued really at all in the 6MOY awards"
I think maybe it's just not considered very valuable in general - not these days at least. It's not just the 6MOY voters that don't place much value on what Ed does, it's also GMs league wide. Otherwise, someone other than BRK would have swooped in and snatched him up. There just isn't a big market for traditional back up centers in today's NBA.
BNM