Just swapped my Pirelli Cinturato SF2 All Seasons to summer tires and noticed that the inner surface of Pirellis is uneven with some kind of bulging from side to side

Never seen this before, all four wheels are affected though not to the same degree. No visible defects on the outer surface.

The tires are ~5 months old with roughly 5K miles on them, they look like new outside. Wheels were balanced and aligned in December.

Is this normal? Shall I contact the shop/manufacturer?

Photos:
https://bit.ly/3a4chRX

https://bit.ly/3LcVOaI

https://bit.ly/3yzR2RU