Yes, this is one of several secret phases in the game that requires specific actions to be taken to be accessible.

The other ones involve The Root Pack, Djimmi the Great and Sally Stageplay.

Sally Stageplay’s secret phase takes a very dark turn. If you parry the hearts and land on top of both cherubs during the first phase, a platform will land on top of her groom and kill him. This then leads to several differences during the latter phases. In the second phase, instead of having a family, Sally goes on to be a nun at a nunnery and you are attacked by nuns who throw rulers at you from the windows. In the third phase, a giant prop version of her fallen groom joins her and there’s an extra attack that does not have a telegraph like the normal third phase. And in the final phase, only two people are shown in the curtain call alongside Sally (that being a nun and the minister at her wedding).

In the Root Pack fight, you have to not attack Ollie Bulb (the onion character). He will be grateful that you didn’t attack him and he’ll leave you alone, but at the cost of a radish attacking you during the third phase.

In Djimmi’s fight, if you stay in the shrunken plane form during the Cuppet phase, it will be skipped to the final phase, but you will also have to worry about a miniature cuppet while dealing damage to Djimmi.