Not quite - they told us they a fighter had to lock, but that was bolleaux.
A fighter of that era could acquire a target in search mode, it did not need to 'lock on' to acquire. Then just lock and paint the target for the few seconds the missile needed to track towards the target. No 'lock' to 'break' earlier, so energetic maneouvre wouldn't achieve much.
Some of the things we were incorrectly taught would actually have made an interceptor's task easier....
We didn't even know about off-boresight firings.
One trick was to lock in the head sector and watch the result - if you saw evasion you knew the target knew. So you then went back to search, crept round the back and converted to a search stern sidewinder firing...
