our board does the same, using a esp32-c3-mini module. -Not sure if that makes it normal or not.

My design has analog input channels on IO0 and IO1 and a ESP32-C3-MINI-1-N4 module on it.
I have configured the channels with :
ESP_ERROR_CHECK(adc1_config_width(ADC_WIDTH_BIT_DEFAULT));
ESP_ERROR_CHECK(adc1_config_channel_atten(ADC1_CHANNEL_0, ADC_ATTEN_DB_6));
ESP_ERROR_CHECK(adc1_config ...