iTunes backups contain iPhone photos?

It depends on whether or not you have iCloud Photos turned on in the iPhone. If it is on, then they are not included in a backup to a computer (or in] iCloud Backup). See the following from Backup methods for iPhone, iPad, and iPod touch - Apple Support

A computer backup of your device, which is not the same as a sync, includes almost all of your device's data and settings. A backup from a computer doesn't include:

• Content from the iTunes and App Stores, or PDFs downloaded directly to Apple Books
• Content synced from Finder or iTunes, like imported MP3s or CDs, videos, books, and photos
• Data already stored in iCloud, like iCloud Photos, iMessages, and text (SMS) and multimedia (MMS) messages
• Face ID or Touch ID settings
• Apple Pay information and settings
• Apple Mail data
• Activity, Health, and Keychain data (to back up this content, you'll need to use Encrypted Backup in iTunes.)

See Backup methods for iPhone, iPad, and iPod touch - Apple Support. It should be the same for Windows and macOS. Generally anything that is already available via the cloud will be omitted from the device backup. In particular this would include photos if you have enabled iCloud Photo Library.

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