The KB uses the word 'must', and as such I'd support the KB and say yes!
" Recommended Actions
ePO 5.3 and later users must apply the steps in Configurations 1 (A), 1 (B), and Configuration 2 below.
ePO 5.0.x and 5.1.x users must upgrade to ePO 5.1.2, and apply the steps in Configurations 1 (A), 1 (B), and 1 (C) below.
NOTE: These ePO versions are End of Life."
Which points out a concern I have, in that ePO 5.3.x is nearing its EOL as well - EOL: 31/3/19.
ePO End of Life page
An option for you to consider.
If you upgrade to 5.1.3 you can go to 5.9 ... !
Might save you some repeat work for the future!
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Please note though that KB 84628 is only applicable if you are implementing certificate validation - if you're not using this or planning to implement it, you can skip this KB. Having cert validation implemented is not a requirement for updating ePO.
Similarly if your browser cert is already 2048bit, then there's no need to regenerate it - it's only a problem if your ePO installation started life with a 1024bit cert and has been upgraded all the way from there.