Tested with Immersive Weathering only, with Terra, and with Fabric Seasons.
In none of these combinations is thin ice spawning around normal ice.

Minecraft 1.18.2
Fabric 0.14.8
Fabric API 0.58.0
Immersive Weathering 2.5.6

Also, thin ice is easily spotted by their darker blue tint, and WTHIT also displays it as thin ice, instead of ice.
It'd be more immersive and a bigger challenge if thin ice had the same color as normal ice, and would be displayed as normal ice on WTHIT.

Thank you for the great mod though!

Pretty sure this is no longer an issue in the newer versions, it worked on 1.18.2 Quilt a month or so ago