1.2.1+fabric_carpet_1.16 gives confusing errors in 1.16.4

[mrvn]

I'm starting minecraft 1.16.4 from MultiMC. The log shows that fabric/skyblock is removed:

[22:25:00] [main/INFO]: Loading for game Minecraft 1.16.4
[22:25:00] [main/INFO]: [FabricLoader] Loading 5 mods: [email protected], [email protected]+facf3bbf95, [email protected], [email protected], [email protected]+fabric_carpet_1.16
[22:25:00] [main/WARN]: Mod skyblock (1.2.1+fabric_carpet_1.16) does not respect SemVer - comparison support is limited.
[22:25:00] [main/INFO]: SpongePowered MIXIN Subsystem Version=0.8.2 Source=file:/home/mrvn/.local/share/multimc/bin/libraries/net/fabricmc/sponge-mixin/0.8.2+build.24/sponge-mixin-0.8.2+build.24.jar Service=Knot/Fabric Env=CLIENT
[22:25:01] [main/WARN]: Error loading class: net/fabricmc/fabric/impl/registry/sync/RegistrySyncManager (java.lang.ClassNotFoundException: net/fabricmc/fabric/impl/registry/sync/RegistrySyncManager)
[22:25:01] [main/WARN]: @mixin target net.fabricmc.fabric.impl.registry.sync.RegistrySyncManager was not found skyblock.mixins.json:RegistrySyncManagerMixin
[22:25:07] [main/INFO]: Environment: authHost='https://authserver.mojang.com', accountsHost='https://api.mojang.com', sessionHost='https://sessionserver.mojang.com', servicesHost='https://api.minecraftservices.com', name='PROD'
[22:25:08] [main/INFO]: Setting user: mrvn23
[22:25:08] [main/INFO]: Backend library: LWJGL version 3.2.2 build 10
[22:25:09] [main/WARN]: Removed resource pack fabric/skyblock from options because it is no longer compatible
[22:25:10] [main/INFO]: Narrator library successfully loaded
[22:25:10] [main/INFO]: Reloading ResourceManager: Default, Fabric Resource Loader (v0), Fabric Loader, Carpet Mod in Fabric, SkyBlock
[22:25:19] [main/INFO]: OpenAL initialized.
[22:25:19] [main/INFO]: Sound engine started

I used the following mods:
fabric-carpet-1.16.4-1.4.21+v201216.jar
skyblock-fc-1.16.4-1.2.1.jar

Note: starting a map gives an empty map so it seems to work despite the warnings, it's just confusing.