“Oracle Instant Client” for Linux x86-64 (RPM) – why not “*.so.X.2”?

Why is this:

10.2.0.5 (why not “.so.10.2“?):

• ./usr/lib/oracle/10.2.0.5/client64/lib/libocci.so.10.1
• ./usr/lib/oracle/10.2.0.5/client64/lib/libclntsh.so.10.1
• ./usr/lib/oracle/10.2.0.5/client64/lib/libclntsh.so -> libclntsh.so.10.1
• ./usr/lib/oracle/10.2.0.5/client64/lib/libocci.so -> libocci.so.10.1
• ./usr/lib/oracle/10.2.0.5/client/lib/libsqora.so.10.1

11.2.0.2.0 (why not “.so.11.2“?):

• ./usr/lib/oracle/11.2/client64/lib/libocci.so.11.1
• ./usr/lib/oracle/11.2/client64/lib/libclntsh.so.11.1
• ./usr/lib/oracle/11.2/client64/lib/libclntsh.so -> libclntsh.so.11.1
• ./usr/lib/oracle/11.2/client64/lib/libocci.so -> libocci.so.11.1
• ./usr/lib/oracle/11.2/client64/lib/libsqora.so.11.1

11.2.0.4.0 (why not “.so.11.2“?):

• ./usr/lib/oracle/11.2/client64/lib/libocci.so.11.1
• ./usr/lib/oracle/11.2/client64/lib/libclntsh.so.11.1
• ./usr/lib/oracle/11.2/client64/lib/libclntsh.so -> libclntsh.so.11.1
• ./usr/lib/oracle/11.2/client64/lib/libocci.so -> libocci.so.11.1
• ./usr/lib/oracle/11.2/client64/lib/libsqora.so.11.1

12.2.0.1.0 (why not “.so.12.2“?):

• ./usr/lib/oracle/12.2/client64/lib/libocci.so.12.1
• ./usr/lib/oracle/12.2/client64/lib/libclntshcore.so.12.1
• ./usr/lib/oracle/12.2/client64/lib/libclntsh.so.12.1
• ./usr/lib/oracle/12.2/client64/lib/libclntshcore.so -> libclntshcore.so.12.1
• ./usr/lib/oracle/12.2/client64/lib/libclntsh.so -> libclntsh.so.12.1
• ./usr/lib/oracle/12.2/client64/lib/libocci.so -> libocci.so.12.1
• ./usr/lib/oracle/12.2/client64/lib/libsqora.so.12.1

The “.so.X.1” links even get described here:

• http://www.oracle.com/technetwork/topics/linuxx86-64soft-092277.html#ic_x64_inst