I haven't seen SE mention anything stating their intent was to have players vary their play. They said they want players to choose how they earn the tomestones from our normal options.
If a player chooses only what they consider to be the most efficient route, then that's what they do. If someone wants it to be grindy, they can always run the same trial 100+ times. It's a decision the player gets to make for themselves instead of SE making it for them.
Trying to force players into specific content may result in the player not participating at all, which can lead to other problems.
There is no automatic win strategy to adopt because different players want different things. If SE's own goal is to increase player participation, this is the best way to go because the player has some control over what they do.
As many complaints as we've heard about the tomestone design, I don't think I've heard anyone say "I'm not going to participate in this because it's just a tomestone grind". That's not to say that there aren't a few, I'd be surprised if there weren't, but it doesn't seem to really be discouraging anyone from participating.
On the other hand, players who have skipped the relics in the past because they didn't like the content they were asked to do or thought it was too grindy are participating this time because they're getting to choose content that is fun to them. Because it's become fun instead of tedious, they're taking an interest in it.
Was this experiment a success in their eyes? We'll have to see how the relic series is designed next expansion assuming they don't give us a specific answer in some interview before then.
