Dada Sarvatmanandji himself introduced / re-introduced this quote in October 1990 because at that time he was the organisation. He ruled over everything and he thought that by this quote everyone will be convinced fully to blindly follow and execute his order. This fake quote suited his needs well. Other Dadas who helped him in this regard included: Bhaveshanandji, Tadbhavanandji, Vratishvaranandji, Vijayanandji, Mantreshvaranandji, among others.
Some naive people may justify that the terms "mission" and "organisation" are two different things; but, practically speaking, they are not. In Bengal, mission means organisation such as the Ramakrishna Mission. And not just Bengal, the world over people talk about the Christian Missions. In these cases, they are talking about the Ramakrishna organisaton comprised of people and projects and the Christian mission comprised of people and projects. In common parlance mission means organisation.
And indeed if you read the propagandised quote it carries the same meaning - that mission is an organisation where people gather and work:
"If you want to know me, work for my mission, because I have merged myself with my mission."
So it was in that spirit, whereby mission means organisation, that Sarvatmanandji created this fake quote. His intent was: Baba has merged in the mission (i.e. organisation) and the way to please Him is to work for the organisation and follow your higher authority. This was Sarvatmanandji's plan for keeping all power concentrated in his hands. Remember, back in late October 1990, the whole of AMPS was very different - it was a monolithic structure under the dictatorship of one person. It was not fractured; there was one person the top seat. And indeed the plan worked; nobody opposed Dada Sarvatmananda.
Here is the proof: Just a few days later Central Committee unanimously declared the Mahaprayan Divas observance as an annual pilgrimmage to Tiljala - thereby making Kolkata the focal point. The mandate was for all to come to Tiljala to observe so-called Mahaprayan; it was not allowed to observe this anywhere else - only Tiljala (Kolkata.)
Hence, just as those Hindu priests fabricated one tale that Mahaprabhu merged into the Jagannath idol in order to appease and control all his disciples, similarly Sarvatmanandji concocted that false merge in mission quote and attributed it to Baba to eyewash legions of margiis and wts. Sarvatmanandji's plan was that they should follow his every word because he (Dada Sarvatmananda) was the organisational head and Baba had merged Himself into the mission / organisation.
And we can see that Sarvatmanandji got success.
In the next few short years, he carried out so many dastardly deeds by his mere order: Mahaprayan dogma, Fake Ananda Vaniis, Expulsion as a weapon and so much more. Sarvatmanandji did so many things because he had harnessed the obedience of workers and margiis by concocting this single quote: "If you want to know me, work for my mission, because I have merged myself with my mission." For this reason, so many listened to his every word and followed his command.
What then is the difference between Dada Sarvatmananda's approach and that of those dogmatic priests of the Puri temple. Both fabricated outrageous tales in order to bring scores of followers under their control.
I think now the point is clear.