Yes, unfortunately it is, and the lawyer who promised otherwise was not being straight with you.
Facility designation in the federal system is controlled entirely by the Bureau of Prisons Designation and Sentence Computation Center in Grand Prairie, Texas. Nobody outside of that office has binding authority over where an inmate gets placed. Not the sentencing judge, not the defense attorney, not the prosecutor. The judge can recommend a facility close to the inmate's home address in the sentencing order, and that recommendation carries some weight, but it is exactly that: a recommendation. The BOP is not required to follow it.
There are several legitimate reasons your son could end up in Colorado rather than Texas. The most common is bed space. Federal facilities run at or near capacity consistently, and inmates get placed where there is room within the appropriate security level. Another possibility is a separatee designation, which means a co-defendant or someone connected to his case is already housed at the Texas facility he or his attorney requested, and policy requires them to be kept apart. Colorado also happens to have a facility at ADX Florence for serious cases, but it also has two federal prison camps, which are the lowest security level available and house nonviolent short-timers. Depending on his security score, a camp placement is not a bad outcome even if the location is not ideal.
On the attorney issue, the hard truth is that federal defense lawyers who promise facility placement are promising something they cannot deliver. The sentencing judge cannot deliver it either. If your son was going to plead out regardless, the value of expensive private counsel was always limited. That is a conversation worth having honestly before the next time the family faces a legal situation.
The good news is that after 18 months he can apply for a facility transfer closer to home. That process is not guaranteed, but it is a real option worth pursuing when the time comes.