Why I couldn't guess but an example similar to the article that I tried does not immediately execute (version 5.2.37(1)-release) when indrected through a variable as you show although other aritmetic evaluation does still happen when indirected. You can echo "${num}" and it shows the passed string. If you change it to declare -i num ; num="${1}" then it does immediately execute.
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Why I couldn't guess but an example similar to the article that I tried does not immediately execute (version 5.2.37(1)-release) when indrected through a variable as you show although other aritmetic evaluation does still happen when indirected. You can echo "${num}" and it shows the passed string. If you change it to declare -i num ; num="${1}" then it does immediately execute.