There is a one-off line from Linus in the early days, and some interpretable evidence in its design, that suggests this is true.

It's not what I would call strong evidence, but then again: if you're building an API without a clear consumer, it'd be worthwhile to build your own consumer too. Especially if you're your own market.

My understanding from reviewing the history is more that Linus wrote enough of git for him to be able to use it himself and then said "If other people want to use this, they may need to add some porcelain on top of it"

There then were a couple different porcelains written and discarded in favor of what we have now.