It is and it isn't. Ultimately when designing the level I usually want the player to have an "aha!" moment, or to feel like they have figured something out or discovered something - whether that's the thing I intended when I made the level or not.
As a solver, something that really takes me out of that experience is when multiple levels fall into what I feel like are an "overcentralised" area of the solutions. To me this is a set of particularly powerful skill interactions that levels (especially harder ones) can tend to gravitate towards that are typically most efficient. If you as the player know these, then a lot of easier levels can just be solved that way too without really engaging with the level. Some of the worst offenders of these are:
- Cancelling a basher or miner to sneak up/through a wall somewhere
- Using a digger on a hill to create an unclimbable wall
- Using some of the more 'obscure' blocker interactions
- Adjusing the RR to reverse a lemming with overlapping builders
As the quote goes "Given the opportunity, players will optimize the fun out of a game", and I think that when you know about those interactions it can be very hard to not just reach for the same interactions over and over. When designing levels I really try to create variety in the solutions which I need to rule out many of the most powerful interactions to give others room to shine - but this is really hard because alot of these interactions can just be used everywhere. I want each level to really feel different when solving it, which means the ways the skills interact in the level have to be unique. I will be much harder on a backroute to a level if it lets you solve a level in exactly the same way as a previous one, or in a way that I feel makes the level boring.
A last point on this is that I think there is a degree of trust that builds up between the player and designer as they play through the pack. If i've played a pack and reached the hardest levels, I get a feel for how those levels are put together and trust that the designer won't throw some really unfair/unfun solution at me to make the level harder (e.g. find the exact RR or try again after 5 minutes solving again) - this trust lets me instead focus on finding a 'logical path' to the solution. I want my levels to build up trust in that way too - I won't throw every evil trick I have at you in one level. If you get any particularly 'clever' interaction it WILL be the 'aha!' moment of the level, and I won't red-herring you away from it - Instead I'll try and give you every opportunity to find it, and streamline the level to make needing to save that crucial skill something you discover early.
At the end of the day, the level should make the player feel good for solving it.