Depends on how the enclosure is designed.
Some enclosures that are eSATA only don't have any electronics in them at all ... just a cable that connects the eSATA external port to an internal SATA pigtail. These enclosures should not have any size limit.
Other enclosures that offer eSATA also have a 1394 or USB external connection, or have the ability to use an IDE/PATA drive inside rather than SATA. For these enclosures, the electronics that are doing the interface bridging can impose a size limitation.
Conceivably, some enclosures might state a size limit to ensure that you only use lower capacity drives, which run cooler, and are therefore within the enclosure's thermal limitations. I would say these enclosures would be marginal for any use in the first place.