Plugin grabber is very slow compared to rendering to sample

I’m rendering a plugin to a new instrument, it’s set up to render a single sample for ~3 seconds, looping is not set. It takes about 3 seconds to finish. When I set up a note in the sequencer for 3 seconds and render it, it completes in the blink of an eye.

I did another test with 10 seconds, and the sequencer render to sample took about a second, whereas render plugin to samples took about 10 seconds.

It’s almost as if render plugin to sample is happening in real time rather than using an offline render.

Is that the case? And if so, is there a way to offline render so that it goes a lot faster? I want to render a bunch of bigger instruments, and would prefer if it went faster like it does on sequencer render.