There is a major difference between the openness of the Librem 5 (L5) vs Android phones. The L5 is the first phone with free/open source schematics (GPL 3.0) for its circuit boards since the Golden Delicious GTA04A4 which was released in Jan 2012. Purism has only released the STL files for the L5's case and the board schematics in PDF, so it would take some work to recreate the original CAD files, but anybody can legally reproduce the hardware in the L5. To find a phone which released its CAD files, you have to go back to the OpenMoko Neo FreeRunner released in June 2008.
Purism has also released the board view images to show where components are placed on the L5's boards. You may be able to find the board view for a few models (such as iPhones), because they get leaked, but as far as I know, no Android phone manufacturer publicly releases the board views of their circuit boards.
If your argument is that the circuit boards don't matter, because most of the functionality is locked up in proprietary chips, then let's look at the chips that Purism selected and see if there's a difference. Qualcomm, MediaTek, UNISOC and Samsung don't release the documentation for their mobile application processors without an NDA, and Apple and Huawei don't release their documentation on their chips to any outside companies as far as I know. In contrast, NXP released 7000 pages of documentation plus their Android and Linux software for the i.MX 8M Quad to anyone who registers on their website. They restrict the security manual to only certain approved people, but everything else can be obtained and NXP has a public forum where anyone can ask questions about their i.MX processors. Likewise, Thales releases the documentation on the PLS8 cellular modem and provides a public forum.
Android phones commonly have a locked bootloader which prevents the user from changing the OS. All Huawei and Apple phones have the bootloader locked. Most Samsung phone require using an unauthorized crack. Motorola and Xiaomi require applying for an unlock code code and waiting up to two weeks for it and using it voids the hardware's warranty. Sony makes it easy but voids the warranty. Google also makes it easy, but won't honor the warranty unless the Pixel is reflashed to the original OS and relocked. In contrast, the Librem 5 has such restrictions.
Another issue is the drivers and kernels. Qualcomm has the best track record of the major mobile SoC manufacturers since it provides public access and the commit record to its kernel source code at Code Aurora, but the community has to take that code and adapt it to work in mainline Linux and it often takes 3 or 4 years to fully support Snapdragons. Samsung has done better in recent years, but MediaTek, UNISOC, Huawei and Apple are horrible. However, NXP is far better than all these since it commits directly to mainline Linux and is willing to work with the community to support its chips.
Purism develops its code in public and encourages its developers to interact with the community. All the firmware in the L5 is proprietary, but it is worth mentioning that Purism is planning on using FOSS firmware in its secondary Cortex processor to control the smartcard reader. Also the OpenPGP specification is open, so anyone can study it.
I would argue that all of these things add up to make the Librem 5 the most open phone that can be bought today (with the PinePhone a close second). I have a problem with some of Purism's marketing, like the "100% made in the USA electronics" slogan for the Librem 5 USA, but you have to look at this in the context of the actual mobile industry and what is possible in the real world. Sure it would be great to have a phone with open hardware chips, but you are talking about hundreds of millions of dollars to develop those chips and paying hundreds of millions more to license the necessary IP, which is totally unrealistic.