I do not see it either. Too many variables to make such a broad blanket statement.
In general, you may practice your own patent[process of making or using 'x'] but still infringe a dominating patent that claims 'x' as a composition. An objectively high likelihood that acts will constitute infringement is the general test---judges of course have considerable discretion in increasing a damages award. Courts will look to objective recklessness on part of infringer that avoids its duty of care to not commit the tort.