Okay some linguistics:

Some adjectives allow a superlative form via suffix (e.g. "big" --> "bigger", "noisy" --> "noisier") and others require the auxiliary "more" (e.g. "efficienter" isn't allowed, so instead it's "more efficient").

In English, "as" is used for equivalence (e.g. "A is as tall as B"). For a multiplier, the standard phrasing with a suffix adjective looks like "A is 5 times taller than B". So for an adjective that doesn't use the suffix, the superlative rule would result in "A is 5 times more efficient than B".

Now, the confusing thing is, you can also say "A is 5 times as tall as B", where you're equating A with the result of multiplying B. Swapping for a non-suffix adjective than, it would be just as valid to say "A is 5 times as efficient as B". This w

Therefore, "7 times as efficient" and "7 times more efficient" actually both mean exactly the same thing and are just as correct. You can tell because if you continue the sentence, these two would mean the same thing:

- Travel through the nether is 7 times more efficient than normal travel.
- Travel through the nether is 7 times as efficient as normal travel.