Minecraft loses 18,446,462,598,732,840,960 seeds, resulting a total of 281,474,976,710,656 seeds, for 1.18. Here are the seeds and screenshots of these happenings.

Seed 1 - original

Seed 281474976710657 - almost identical, though different tree locations and biome boundaries.

Seed -7379792620528906220 - different biomes and expected shadow seed

Expected result: It should have 2^64 seeds, edit: including shadow seeds.

Observed result: It has 2^48 seeds.