These attempts to "join religions" is nonsense that is explicitly motivated by somebody's need to devalue all religions.
People of true faith should have zero need to adjust their observances for the sake of communing with those of opposing faiths.
Someone once said there are only a couple of choices when it comes to assessing who Jesus is: Liar, Lunatic, or Lord. There are no other choices. If he is a liar, shame on Him. If is He is a lunatic, pity Him. But if He is Lord, bow down and worship Him and Him alone. Because, if He is Lord, that excludes all other religions that perceive of Him as anything else.
As my daddy use to say, "there are only two kinds of people in this world: 'saints' and 'aints'."