I don't want to retread this, since we already discussed this upthread, but this isn't correct - that's not what the rule says - and
@chrcoluk is correct that even pure reliability changes also allow increased performance. Interested readers can go and find the previous discussion.
Well you better go tell a lot of F1 engineers you know better than they do, as how I have explained it, is exactly how many have explained it to me when I asked ex colleagues how they see the rules being implemented this year.
Changes WILL ONLY be allowed that effect reliability and safety, if increased performance is deemed to be a main result, the changes will not be allowed.
There would be zero point in an engine feeeze, if manufacturers just built unreliable engines, knowing they can change things later and get better performance.
Which is exactly why any submitted changes will be shown to the other engine manufacturers so they can veto the change if they believe it will result in a noticeable increse in performance.
All manufacturers know this, so they basically self police themselves, possibly why we have seen very reliable engines all through testing.