Assuming you convert immediately after funding the traditional IRA, is there any reason NOT to convert to a Roth since it wouldn't be a tax event? (Income too high to qualify for Roth straight up or deduct traditional IRA contributions)

Do you already have another IRA with funds in it? If not, then no, you should roll it over. If you do, you can still roll over, but it won't all be tax free.

Learned this lesson the hard way when I started working on my 2022 taxes.

I rolled a 403b over to my financial advisors' firm, and it didn't click that it went from a 403b to an IRA

I did my backdoor Roth contribution like I always do.

Now I owe taxes on that $6k because the IRS lumps all of your traditional IRA accounts together. So even though my $6k was an after-tax contribution, all of the money in the 403b rollover IRA was pre-tax.

Not only is this costing me about $1400 in taxes (almost my entire refund), it's been a real PITA to figure out how to account for it all properly in TurboTax.

I will eventually get some (hopefully most) of those taxes back when I take distributions from the IRA, but that's a good 15 years away.

The way around this, if it's an issue for you, is to contribute to a mega backdoor Roth, if your company allows it. That's where my 2023 contribution will be going. And the mega backdoor Roth is not capped at $6500; its cap is tied to the $66k cap on total 401k contributions.

Sucks, but $1400 20 years from now won't matter near as much as having the tax free growth inside of the Roth.

However, under Reg BI your advisor should have educated you on this (as a potential reason not to do the rollover) before recommending the rollover.

They tried. It was a misunderstanding on my part. I procrastinated on opening the mega backdoor. That would have avoided the tax hit.