Reg D and HSA accounts

Can anyone give me some insights on how Reg D applies to HSA accounts with regard to debit card transactions? Are HSA accounts restricted to the 6 total debit card transactions per month just as regular savings accounts are? For some reason I thought that HSA accounts were exempt from Reg D but I've gotten conflicting information. So other thoughts would be greatly appreciated!

Arguably, HSAs are exempt from Regulation E because they are technically a trust account.

If HSA funds are held in a savings account, that savings account is subject to Regulation D. Savings accounts are subject to Regulation D's restrictions on activity regardless of who owns them.

Most HSA Accounts are actually booked on systems as checking accounts, and consequently, there are no restriction limitations.