I am not petting them daily, because they are still on 5 hearts. But you're saying you still need to pet them daily even though they are on 5 hearts to let them grow daily?
On the wiki it says this:" Sheep who eat every day mature after 4 days. Sheep can be sheared for their
Wool when their coat grows in.
Shears must be purchased at
Marnie's Ranch. A sheep will normally grow in its coat every 3rd day if it has been fed and has at least 70 happiness. The
Shepherd Profession reduces coat grow time by one day.
Having 900 or more Friendship (4.5 Hearts) reduces the time it takes a sheep to grow its coat by a further day, meaning a sheep can grow its coat every day".
But it never says anyhting about petting them daily.