The concern about moving full-time employees to part-time status is not a myth or over reaction. It's based on empirical historical evidence provided by what began in 2007 and 2008 following the financial crash. Following the crash, employers moved full-time employees to part-time status to reduce costs by eliminating the cost of benefits.
This was the evidence used to predict what would happen due to the PPACA's requirements. It is also the reason that the Teamsters and many other Unions, who originally gave unrestricted, and what is now proven to be
unrequited, support to the PPACA, to send open letters to the President with concerns over a mirrored reaction of what began in '07 and '08.
The trend to reduce benefits costs has been in place since '07, and that was before the mandates of the PPACA. As has been stated above by others, there are many variables in the employment numbers that can account for any short term trend, either up or down. Only long term analysis will prove out whether the PPACA will have long lasting or a potential permanent affect on employment practices.
Employers, as also been said before by another poster, will make their decision based on the bottom line to the company. They have a fiduciary responsibility to the stock holders to do whatever is required to reduce costs and maintain profitability. This includes the option of moving full-time employees to part-time status. This is also made possible by the establishment of the government exchanges, giving the employers the ability to garner emotional, moral and ethical cover, given that their employees will still have access to health care insurance, when they lose their employer provided insurance.
If we look beyond the politically motivated arguments from both sides, and look solely at the facts, market trends and basic business practices, the concern, as I said at first, is not a myth or overreaction. It's based on empirical historical evidence, and current trends in hiring practices.
And, in addition to the problem with employment status, the Unions have additional concerns (and this from a source that the OP should believe):