The question was disadvantages to numbering rooms.
There is one disadvantage I can think of: If the interior walls are expected to change, Or the number of employees is expected to grow a lot before the lease is up: Numbers an make the changes even more confusing.
I have seen companies turn a conference room into new offices. Now you could have the problem that conference room was #007, but now one of the new rooms will be 007 1/2 or 007A.
I have also seen closets turned into office space. If you forgot to number the closet, now you have to stuff two people into an unnumbered space, and describe it as the 2nd unnumbered door after #007.
Turning offices into conference rooms or senior mangers offices results in the need to skip a number.
All these changes result in confusion. Employees room numbers change without them moving, others refer to the space as "we are meeting in room which used to be #007 before Joe retired and they redid the floor when the new CEO was hired"
The advantages are many: navigation, logistics. These are so important once the lack of room identification it is time to develop a numbering or naming scheme.
Keep in mind that employees may start to name the rooms themselves. They will say "I see you were assigned Sean's old office, he was here long before Daniel"