Frequently I share photos with friends or save them on my iPad after doing a quick series of edits to one or multiple photos.
While sometimes the Share button becomes greyed out while a photo's recent edits are being synced, sometimes that button becomes available and it's visibly before the photo actually *can* be exported because the operation tends to fail after a few seconds.
Export > Share To... should be a queued operation. If there are pending edits to sync, then the operation should be queued after edit sync takes place and proceed as intended. Otherwise at the very least the Export options as a whole should be temporarily disabled.