But they were not.
Here's a few reasons why what they did was dishonest and unnecessary:
1. As has been demonstrated from the thread, when asked if they believe in it, they said they would like to. Not do.
2. When asked about faith, they said they had faith of a mustard seed - that's a tiny amount - but it's directly what Jesus said the amount of faith is needed to move mountains. By using that, they were in effect saying they had a significant amount of faith. They did not.
3. They were baptised. To be baptised as a Mormon requires professing belief in the message that Joseph Smith brought, along the following prophets of Mormonism, as well as Jesus' visit to the Americas, that the Church of Jesus Christ of Latter Day Saints is the True Church, and so on. If you were to go along to a Mormon church and they asked you that before the baptism - as they do - I have first hand experience of this as I visited a Mormon church to learn more about it, and they asked if I believed in the message of Mormonism - if you say no or that you have your doubts, then they will not baptise you. Nor will they ostracise you or keep bringing it up.
The very fact that they were baptised shows that at the very least they were dishonest and secretive about their actual beliefs.
4. It says they did tell their elders. Later - but not before as we can see from a couple of obvious things.
5. There was no need for them to be baptised if they didn't believe it. It's not like Mormonism is secretive. They won't, as soon as you convert, say, "Right, here's what we REALLY believe, and this is the secret handshake, this is the secret code-word, and if you tell anyone we'll punish you".
6. The claims of it being necessary as one suggested because the more information they have the better is moot. There have been a fair few Mormons who have lost their faith and have told their stories.
7. Being baptised does not give you access to any hidden doctrines. I read the Book of Mormon, Pearl of Great Price, and Doctrine of Covenants as a non-Mormon, and discussed Mormon theology freely. They were never secretive about what they believed. Naturally not everyone knew the answer to what I asked, but they would always answer what they could, and suggest someone who could if not.
8. If they were going the whole hog to places of worship and doing everything like them, why didn't they go and be baptised as Sikhs? Why not as Jewish converts?
Thus, as we can see, their deception was unnecessary and uncalled for.
Hope it makes it a bit clearer.