Absolutely right. EAccelerator for PHP caches compiled PHP pages ONLY when running in a persistent (DSO/FCGID) manner .
Moreover, eAccelerator with Zend Optimizer - eAcc is reported to work with Zend Optimizer's loader. Zend Optimizer must be installed after eAccelerator in php.ini so it's loaded after eAccelerator. If you don't use scripts encoded with Zend Encoder then it isn't recommended to install Zend Optimizer with eAccelerator, and it won't give you any extra performance.