Nginx - errors in log due to missing kernel syscall?

Software SW bugs discussion
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I am running nginx in an Alpine 3.13 LXC container. I can see in the error.log following entries (seems two of it per start)

[emerg] 324#324: io_setup() failed (38: Function not implemented)

I assume it means there is missing kernel syscall #38. According to e.g.this table https://filippo.io/linux-syscall-table/ number 38 should be setitimer, and in the source code of nginx I can see this method is really used.

If I was right my question would be is this a bug or is this method missing in the omnia kernel intentionally?

cat /etc/turris-version
5.1.8
cat /proc/version
Linux version 4.14.216 (packaging@turris.cz) (gcc version 7.5.0 (OpenWrt GCC 7.5.0 11f4918)) #0 SMP Tue Jan 26 07:47:52 2021