Doctor is being really pushy about Entyvio

I started going to a new GI doc last year and after getting my colonoscopy results back he told me I had pretty severe ulcerative colitis and recommended switching from the Mesalamine I'd been taking for years to Entyvio.

From the getgo it felt like he was being really pushy about it. I was immediately suspicious of it because it just felt off and I know that there are people whose entire jobs are to lobby for medication and treatments on behalf of pharmaciutical companies, with my understanding being that there's usually some sort of kick-back for doctors who recommend them.

I pushed back for staying on the Mesalamine for a few months before I had a bit of a flare-up and decided to give it a shot since my insurance deductible had been more than met. I've been on it for about 3 months (just got my first maintenance dose after the ramp-up period the other month), but at the very best it's no better than the Mesalamine, but realistically it's kinda worse because it will sometimes give me headaches and has resulted in some weight gain. FWIW even just the past couple weeks I've been having more abdominal pain, nausea, and irregular BMs, but that could also just be symptomatic of a flare up.

I just got back from a visit to discuss all of this with my GI doc because I think I'd rather go back on the Mesalamine because it was generally working, and because I'd also like to avoid the [what I imagine to be] high cost of the infusion having just restarted my deductible this year, and he basically said he's not going to do that. He's telling me now that I need to wait 6 months before I really know if it's working or not, despite things honestly starting to trend downward. I confronted him about the fact that that's not what I was told previously, and told him directly that it's all felt very pushy and that now I feel like I'm being gatekept from the treatment that was working for me previously, but he just kept telling me I "can do whatever I want, he's just there to advise me" while not letting me go back on what was working better previously.

Anyone had a similar experience? There seems to be a lot of buzz about Entyvio here in general and it all makes me wonder if there is some shilling happening here, honestly.