-force_key_frames + FFMPEG +FFMPEG+FFMPEG

Question

当使用编解码器h264_nvenc时，FFmpeg省略选项-force_key_frames "expr:gte(t，n_forced*5)“。为什么？是个bug吗？

fmpeg -v verbose -hwaccel auto -i granito.mp4 \
-vf "hwupload_cuda,scale_npp=w=-2:h=720:format=yuv420p:interp_algo=lanczos,hwdownload,format=yuv420p" \
-vcodec h264_nvenc -zerolatency 1 -gpu 0 -profile:v main -level 4.2 \
-preset llhq -bf:v 2 -rc vbr_hq -maxrate 500k -bufsize 1m -acodec aac -ar 22050 \
-b:a 64k -hls_time 2 -hls_list_size 0 \
-force_key_frames "expr:gte(t,n_forced*5)" -sc_threshold 0 -f hls index.m3u8