The "spontaneous" effect is just the natural change of population that we all know about. When the city has unemployment, the population goes down a bit. The opposite case, when there is no unemployment, the population grows. The effect is not as strong as the one from projects, and if the project for expanding the city is used, those natural changes are "overwriten".
About "inflating" the inmigration. Any unit that is not producing and selling, is basically a "burden" for the budget. If you are paying wages for your workers to scratch their bellies at full-time, that unit is a source of wages, but it doesn't generate any tax itself, it doesn't create wealth. Labs are slightly different, because they do not produce anything themselves, but the average skill of workers can affect the average education level in the city (just for natural growth, projects would overwrite it). They also provide good wages.
So, yes, it is better to avoid inmigration if their workplaces are not productive ones. (They generate more retailing, but if the market is not too developed, it would generate more harm than income.)
The massive natural rising of wages was surely due to some enterprisers increasing wages instead of training workers, so they would have higher skill in less time. As the population is rather small, that part of the enterprises affected the average salary. Smaller cities are easier to manipulate if they don't have a mayor to overwrite the changes with municipal projects. |