The bill has been presented by those putting it forward as being what is required. If they are thinking getting it passed, and then let's change it bit by bit then there is an intentional use of a slippery slope policy.
I don't agree with your characterisation. It seems to me it's just caution. The phrase "slippery slope" implies an inevitable "slide" towards unregulated assisted dying. The reality is that, once this law has been passed (if it is passed), any future lifting of restrictions will be subject to similar levels of debate and scrutiny. For example, I believe that the six month life expectancy clause is unnecessary, in fact I would argue it is morally reprehensible. However, it is for people like me to advocate that and persuade parliament to change the law, which will be just as hard as this first phase. Nobody will be saying "well, we've come this far, we might as well just remove that restriction".
The slippery slope fallacy is called a fallacy because it implies an inevitable slide into some undesirable state. The reality is that persuasive arguments have to be made for further change to occur.