Why would you call colocation "building your own data center"? You could call it "colocation" or "renting space in a data center". What are you building? You're racking. Can you say what you mean?
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I think you're failing to understand the meaning and the point of "building your own datacenter".
Yes, you can talk about your office all you'd like. Much like OP can talk about there server farm and their backend infrastructure.
What you cannot talk about is your own office center. You do not own it. You rent office space. You only have a small fraction of the work required to operate an office, because you effectively offloaded the hard part to your landlord.