Not so.
In 1877 the Royal Navy used a Whitehead torpedo against Huáscar. The Torpedo Ram HMS Polyphemus (supposedly the model for Wells' HMS Thunderchild) was launched in 1881.
And the armored ram as a viable weapon in combat was done by that period, though the designers knew it not
Guns had improved enough that rams were not the only way to penetrate armor
The armored ram period is usually considered to have ended in 1870 or so, by that time effective battleship designs with good heavy guns started appearing and the need to ram was gone, though designers kept putting them on just in case
While the Whitehead was around in 1870 it did not become a viable weapon until an improved version later in the decade
There is a reason only one vessel of Polyphemus's type was built and it was not part of the armored ram period but an experiment at reviving the concept after the period was over
In any case I was always talking about modern torpedoes to explain why no one built a solid AP torpedo or has plans to do so