Internally, 8086 and 8088 are the same. They have an 8 byte instruction queue. When the queue is empty, processor stalls while instruction is fetched.
Difference is BIU Bus Interface Unit, which fetches bytes for 8088 and words (2 bytes) for 8086. Each processor takes 4 clock cycles to access RAM.
If we have a fast word instruction, the 8088 will take 8 clock cycles to execute it. The 8086 will take 4 (possibly 5)6 clock cycles if the instruction is word addressed or 8 clock cycles if the instruction is across two bytes. The wiki is assuming optimum storage.
4 clock cycles to fetch and 2 to execute. For a word aligned instruction, the first byte tells processor the type of instruction, and the second specifies the action.
The execution by the EU, knows the instruction is a register based instruction, so it hides execution time for 8088 and odd byte aligned 8086, which means 8 clock cycles.