Yes, that's the confusing part. In actuality you've not changed any of the "performance" parameters that are part of the presets, so the radio button goes back to any of the below you chose. Rest assured though any changed parm does get stored and transmitted to the client on next connect upon hitting save. If not you get a warning.

Standard Settings: Set my profile to the standard settings

Minimum Impact: Set my profile so that it will have a minimal amount of impact on my computer

Maximum Output: Set my profile so that it will do the maximum amount of research possible on my computer

Power Saving: Set my profile so that my computer's power settings can take effect

Only when performance parms are changed does the radio button stick to the below.

Custom Profile: I will customize my profile using the advanced options and settings, and

The Thomases that doubt can compare the preferences screen on the client with the 'custom' view settings on the website, provided you've not changed a single parm locally and saved them. If you did ALL override website profile settings until you clear them.

The client has absolutely no say in which project work units are called. To BOINC WCG is 1 project. Only the web profiles tell the server distribution system what may be send.

I have selected Custom Profile for my machine in the 'Default' profile, increased the number of MIP1 tasks from 3 to 4 two hours ago, then changed the number of MCM1 tasks from 33 to 34 one hour ago. In those past two hours, several MCM1 tasks finished and were uploaded and in return I got some new tasks, but still on my device I'm stuck at 3 MIPs and 33 MCMs, so nothing has changed. The server doesn't propagate the new settings to my device as it has been doing for the past 10 years.
Anyone else seeing this behaviour?
EDIT (7 minutes after my posting): Well, what do you know, the problem has been resolved!

Fri 06 Dec 2019 15:51:07 CET | World Community Grid | Scheduler request completed: got 3 new tasks
Fri 06 Dec 2019 15:51:07 CET | World Community Grid | No tasks are available for the applications you have selected
Fri 06 Dec 2019 15:51:07 CET | World Community Grid | No tasks are available for Smash Childhood Cancer
Fri 06 Dec 2019 15:51:07 CET | World Community Grid | No tasks are available for OpenZika
Fri 06 Dec 2019 15:51:07 CET | World Community Grid | Your preferences allow tasks from applications other than those selected
Fri 06 Dec 2019 15:51:07 CET | World Community Grid | Sending tasks from other applications
Fri 06 Dec 2019 15:51:07 CET | World Community Grid | General prefs: from World Community Grid (last modified 06-Dec-2019 15:42:24)
Fri 06 Dec 2019 15:51:07 CET | World Community Grid | Host location: none
Fri 06 Dec 2019 15:51:07 CET | World Community Grid | General prefs: using your defaults
Fri 06 Dec 2019 15:51:07 CET |  | Reading preferences override file
Fri 06 Dec 2019 15:51:07 CET |  | Preferences:
Fri 06 Dec 2019 15:51:07 CET |  | max memory usage when active: 3914.70 MB
Fri 06 Dec 2019 15:51:07 CET |  | max memory usage when idle: 5872.05 MB
Fri 06 Dec 2019 15:51:07 CET |  | max disk usage: 10.00 GB
Fri 06 Dec 2019 15:51:07 CET |  | (to change preferences, visit a project web site or select Preferences in the Manager)
Fri 06 Dec 2019 15:51:09 CET | World Community Grid | Started download of MCM1_0156630_5396_MCM1_0156630_5396.txt
Fri 06 Dec 2019 15:51:11 CET | World Community Grid | Finished download of MCM1_0156630_5396_MCM1_0156630_5396.txt