Hola.
Yo también tenia la misma necesidad y logre hacer algo como esto, creo que es lo que se requiere ver la cantidad de archivos por curso.
Básicamente lo que hice fue consultar la tabla mdl_logstore_standard_log con el id del curso que del cual requería la información. lo exporte a un excel y filtre solo los eventname "\mod_folder\event\folder_updated" de esta manera los contexid que son los requeridos para identificar los archivos en la tabla mdl_files.
las dos consultas son las siguientes:
select * from mdl_logstore_standard_log where courseid=376
y después de filtrar en un excel los eventname y obtener los contex id la consulta que me dio el numero y el tipo de archivos fue la siguiente:
select * from mdl_files where contextid IN (93161,93172,93173,93171,93174,231896,97603,97604,142870,93169,93175,93175,174301,174301,144005,241307,243331,243331,243331,144456,142870,231896,233564,102229,93175,93175,233564,233564,102229,102229,102229,102229,102229,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,144007,93161,154518,154518,170213,219871,194842,145056,203796,172997,233564,233564,102236,93161,233564,233564,232026,93161,93161,93161,93161,232026,202685,233564,219871,144005,144005,144005,144005,144005,241307,241307,241307,241307,241307,241307,241307,165622,232026,174618,154518,173613,203796,219871,233564,233564,174618,194841,80262,80262,80262,80262,80262,80262,80262,80262,80262,80262,80262,80262,80262,80262,80262,243475,243475,243475,243475,243475,243475,243475,243475,243475,243475,194842,243475,243475,243475,243475,198360,233575,243475,243475,243475,243475,243475,243475,243475,243475,233564,243475,243475,243475,243475,243475,243475,243475,243475,243475,243475,243475,243475,243475,243475,102236,102229,102229,233564,144007,144007,144007,174618,167930,233564,233564,233564,233564,174393,144005,241307,93161,93161,174618,174618,102229,249711,249711,249711,249711,249711,144460,154518,203796,202685,102229,83470,83470,243475,203796,174618,249711,167930,174618,144007,144007,144007,144007,144005,241307,241307,93161,93161,80262,243475,93161,145056,145056,167930,203797,102229,102229,102229,102229,102229,233564,202685,202685,174618,177972,231896,231896,83472,102229,97605,144007,144007,144007,145082,145082,145082,97602,231896,102229,102236,165622,144005,144005,93161,93161,102236,93161,233564,144005,243475,243475,159082,167930,174618,173613,202685,232026,228696,102229,102229,144007,144007,144007,102236,93161,93161,93161,93161,233564,233564,233564,233564,174618,102229,102229,102236,144005,231897,231897,167930,144007,243475,243475,83472,83472,83472,83472,83472,83472,102229,102229,102229,102229,102236,102229,102229,102229,102236,102236,102236,102236,102236,102236,102229,102229,144005,233564,233564,233564,194842,170213,174618,102229,102229,102229,102229,102229,102229,102229,102229,102229,102229,102229,102229,102229,83470,102229,262888,262888,144007,102229,243475,93161,93161,93161,144007,233564,167930,194842,233564,145056,189855,167930,233564,102229,261769,83470,93168,93168,102229,97602,232026,203796,174618,167930,233564,232057,219871,144007,144007,174618,233564,154518,159082,159082,102229,144005,144005,243475,102229,102229,83470,233564,144005,144005,144005,144007,165622,243475,93161,194841,174618,83470,93184,262888,262888,262888,262888,262888,102229
)
Espero que aun que ya es muy tarde pueda servir de algo esta información y alguien que tenga mas experiencia en la BD de moodle pueda optimizar la consulta para no tener que pasar por el excel.