I assume that you are talking about the "RSSI Low Check" feature which can be configured under "Global Parameters" of 802.11a/n/ac and 802.11b/g/n.
Yes, "RSSI Low Check" does not let a client associate if the RSSI is under the configured value. If you actively want to disassociates a "weak" client you have to use the "Optimized Roaming" feature. This last one needs to be enabled globally and uses "coverage hole detection" information and configuration with a 6 db hysteresis. Use "Optimized Roaming" with caution and make sure you do some testing before and after making changes.
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