Is training adaptation reduced when training with different discipline bikes and thus different positions? (ie. road-mtb)

Good day everybody,

I write here today in hopes of resolving a dilemma that has recently come up as I put in more miles on the trainer. I have 2 bikes, one is a nice racing road bike and another is a less nice (but still decent) mtb. I have been using my mtb on the trainer (wahoo kicker core) to do my efforts and the road bike when I ride outside. But I have started to wonder if I am loosing training effectiveness by doing the intervals on the mtb position rather than the road bike position (the one I will be racing in) as they are drastically different; hip angle, Q factor…
I am training to race road u23 elite in Spain which looking at power numbers equates to US cat 1-2 so eking out as much performance is the priority but I was hesitant to beat up the expensive bike on the trainer. Is the performance difference that big?Preformatted text

I look forward to reading your knowledgeable replies, Adrian