No. You are not right. Not even remotely correct. They are both completely capable of solving a problem with multiple variables.
Your question is ambiguous though. Are you asking about independent predictor variables? The answer is: no problems.
Are you asking about multiple parameters to estimate? Again, no problem.
What you don't say is why you think there is any problem at all.
You might be confused because these functions expect a model of the form
fun(params,xdata)
That does not mean that params is a scalar. Nor does it mean that xdata is a vector.
If you have multiple parameters to estimate, params can be a vector or array of any shape or size. If your parameters are split into several distinct variables, then what stops you from combining them into one vector? Nothing.
If you have multiple independent variables, then note that xdata may be an array.
