Yes there is a tire break in period!
New sidewalls are very stiff. That is why tires "plump-up" a few mm after a day or so. Riding the tires allow the tires to reach there final size more quickly by stressing the sidewalls. Once the tires have reached there final width, they will be noticeably more compliant. This seems to happen more with gravel tires than road, and more with tires with anti-puncture material.
I would suggest one ride over 20 miles and waiting 48 hours to break-in. I have not found that higher pressure in the tire matters (other than ensuring the sealant is absorbed). Your second ride will be more comfortable and you'll likely have more handling control. My 50mm Panaracer GravelKing SKs went from 47 to 49mm in 48 hours. My first 40 mile gravel ride with my new tires, when they were 24 hours old, was jarring. I definitely had buyers remorse. The second ride was much better, and it descends like a hardtail mtb!