This is only in reference to those neophytes who have no taste for the exclusive worship of the Lord, known as ananya bhakti. For them this is applicable. Some neophytes have a taste for the worship of different demigods, so our Acharyas advice them to dovetail that into the service of Sri Gaur Krishna in order to elevate themselves. Otherwise even in the Bhagavad Gita Krishna recommends the sincere devotional aspirant to give up all other modes of worship and surrender fearlessly unto His lotus feet alone. But because in the conditioned state many souls have different inclinations, for the sake of their purification...our Acharyas and scriptures find ways to intertwine their particular taste into the service of Sri Hari. This is why Prabhupada uses the term "according to situation" here. This is to help them gradually become elevated to the level of real devotional service.
Just like it is recommended that those who are still aspiring after material acquisitions should approach the Supreme Lord only, for gradual purification.
Neophytes are of many types. The one Prabhupada speaks of here are those who those who are still greatly in contact with the material way of life and haven't yet fully grasped Bhakti tattva. For one who is determined in His resolve to worship only the Supreme Personality of Godhead Sri Gauranga Krishna, Madhavendra Puri describes that even if he is not able to do so properly because of his present conditioned state...there is no fault...Krishna Himself will guide that fortunate soul. He need not seek shelter anywhere else or swerve from His firm resolve of worshipping the lotus feet of Govinda. Madhavendra Puri Himself has composed a verse in this regard, from the viewpoint of a neophyte, begging forgiveness for no longer being able to worship demigods because Vrajendranandan has stolen His heart...even though He is unable to serve His lotus feet properly.
So what then to speak of Nitai Bhakti where Nitai is personally enveloping even gross offenders in the veil of His prema and protection. For those who have already set their heart in the worship of Sri Sri Nitai Gaur and Radha Krishna, there is no need to look elsewhere. On the contrary, it is highly recommended that they remain firmly fixed on the path of swarupa siddhi bhajan.