Yes, that is correct. The Intel HD Graphics driver for Windows will allocate as much memory as is required. This is limited to half of all available memory. For example, a PC with 8GB will make up to 4GB available for graphics usage, as required.
The only time that Windows users should increase the amount of dedicated graphics memory is if they have a poorly-written game that refuses to run unless it sees that a certain amount of dedicated memory is available. There is no performance advantage to dedicating additional memory for graphics.
This message was posted on behalf of Intel Corporation
As N. Scott Pearson mentioned, the Intel® HD Graphics will allocate as much memory as it requires to. This feature can be modified by the system manufacturer so the DVMT can increase or decrease as per the configuration set by the machine. You can always try with a Windows * clean installation in the case that the Microsoft® tools are not working properly or get in touch with them. Additionally, you can try to get in touch with your system manufacturer to check if there is any limitation set on your machine.