mandate that all full time employees be paid for federal holidays if their place of work is closed on those holidays.

Many full-time employees (working more than 20 hours per week) classed variously as "Temps", "Contractors", "Consultants" etc and employed by "Agencies" as W2 Employees receive no paid time off at all and as such are forced to take days off, without pay, when their place of work closes in observance of Federal Holidays.
The days when "consultants" were paid more than their "permanent" colleagues are long gone, they are now used as "cheap labor" by companies wishing to hide the true cost of their labor force.
The "Agencies" employing these "consultants" often charge their client companies rates that are more than double the hourly rate they pay the "consultant", yet they still refuse to provide paid time off even if the "consultant" has worked many years in the same position.